Laser Method for Making Shaped Ceramic Abrasive Particles, Shaped Ceramic Abrasive Particles, and Abrasive Articles

ABSTRACT

A method of making shaped ceramic abrasive particles includes cutting a layer of ceramic precursor material using a laser beam and forming shaped ceramic precursor particles. Further thermal processing provides shaped ceramic abrasive particles. Shaped ceramic abrasive particles producible by the methods and abrasive articles containing them are also disclosed.

TECHNICAL FIELD

The present disclosure relates to abrasive particles, methods for makingabrasive particles, and abrasive articles including abrasive particles.

BACKGROUND

It is known to make shaped ceramic abrasive particles. For example, onemethod includes sequentially: filling cavities on the surface of amicroreplicated tool with a boehmite sol-gel, drying the sol-gel to formshaped boehmite particles within the cavities of the tool, removing theshaped boehmite particles from the cavities of the tool, and thensintering the shaped boehmite particles to form alpha-alumina shapedabrasive particles. While this method is conceptually simple, it istypically quite expensive to make the tool. Moreover, a different toolis desired to make a new desired shape of ceramic shaped abrasiveparticle.

Other methods of making shaped ceramic abrasive particles include ascreen printing technique wherein a sol-gel ceramic precursor materialis screen printed on a substrate, dried to form ceramic shaped abrasiveprecursor particles, removed from the substrate, and sintered to formthe shaped ceramic abrasive particles. While somewhat less expensive,and typically with lower resolution than methods using a microreplicatedtool, this technique still requires the preparation of a separate screenfor each desired shape of the shaped ceramic abrasive particles.

SUMMARY

In one aspect, the present disclosure provides a method comprising:

providing a layer of ceramic precursor material supported on a carrier,wherein the layer of ceramic precursor material comprises a ceramicprecursor and free water; and

cutting through the layer of ceramic precursor material using a laserbeam to provide shaped ceramic precursor particles.

In some embodiments, the method further comprises:

drying the shaped ceramic precursor particles to provide dried shapedceramic precursor particles;

calcining the dried shaped ceramic precursor particles to providecalcined shaped ceramic precursor particles; and

sintering the calcined shaped ceramic precursor particles to provideshaped ceramic abrasive particles.

In some embodiments, the method further comprises:

drying the shaped ceramic precursor particles to provide dried shapedceramic precursor particles;

calcining the dried shaped ceramic precursor particles to providecalcined shaped ceramic precursor particles;

impregnating the calcined shaped ceramic precursor particles with animpregnating composition comprising a mixture comprising a second liquidmedium and at least one of a metal oxide or precursor thereof to provideimpregnated calcined shaped ceramic precursor particles, wherein theimpregnating composition impregnates the calcined shaped ceramicprecursor particles to a lesser degree on surfaces formed by the cuttingof the laser beam than other surfaces of the calcined shaped ceramicprecursor particles; and

optionally sintering the impregnated calcined shaped ceramic precursorparticles to provide shaped ceramic abrasive particles.

In another aspect, the present disclosure provides a method comprising:

providing a layer of ceramic precursor material supported on a carrier,wherein the layer of ceramic precursor material comprises a ceramicprecursor and free water; and

scoring the layer of ceramic precursor material using a laser beam toprovide a scored layer of ceramic precursor material.

In some embodiments, the method further comprises:

breaking the scored layer of ceramic precursor material along scorelines to provide shaped ceramic precursor particles;

calcining the shaped ceramic precursor particles to provide calcinedshaped ceramic precursor particles; and

sintering the calcined shaped ceramic precursor particles to provideshaped ceramic abrasive particles.

In some embodiments, the method further comprises:

drying the scored layer of ceramic precursor material to provide a driedscored layer of ceramic precursor material;

breaking the dried scored layer of ceramic precursor material alongscore lines to provide dried shaped ceramic precursor particles;

calcining the dried shaped ceramic precursor particles to providecalcined shaped ceramic precursor particles; and

sintering the calcined shaped ceramic precursor particles to provideshaped ceramic abrasive particles.

In some embodiments, the layer of ceramic precursor material is providedby partially drying a sol-gel ceramic precursor layer. In someembodiments, the layer of ceramic precursor material is provided bypartially drying a sol-gel ceramic precursor layer. In some embodiments,the layer of ceramic precursor material is substantially nonflowable dueto gravity. In some embodiments, the layer of ceramic precursor materialhas a solids content in a range of from 60 to 70 percent by weight.

Advantageously, methods according to the present disclosure can be usedprepare shaped ceramic abrasive particles without need of expensivemicroreplicated tooling, and can be rapidly and inexpensively convertedbetween desired particle shapes. Further, methods according to thepresent disclosure can be used to prepare shaped ceramic abrasiveparticles that would be prone to cracking during drying usingmicroreplicated tooling or screen printing. Hence, methods of accordingto the present disclosure can be used to prepare shaped ceramic abrasiveparticles that have heretofore been inaccessible on a reliable andeconomical basis.

In yet another aspect, the present disclosure provides shaped ceramicabrasive particles prepared according to any method according thepresent disclosure.

In yet another aspect, the present disclosure provides shaped ceramicabrasive particles, wherein each of the shaped ceramic abrasiveparticles independently comprises a body member and at least threerod-shaped members extending from the body member.

In yet another aspect, the present disclosure provides an abrasivearticle comprising shaped ceramic abrasive particles according to thepresent disclosure adhered with a binder.

In another aspect, the present disclosure provides shaped ceramicabrasive particles, wherein the shaped ceramic abrasive particles aresubstantially planar and comprise a body member and at least threerod-shaped members extending from the body member. In some embodiments,each one of the at least three rod-shaped members has a cross-sectionalprofile independently selected from a circle, an ellipse, a square, arectangle, or a triangle.

Depending on conditions, various unusual shapes of shaped ceramicabrasive particles can be made by methods according to the presentdisclosure. For example, in some embodiments, the at least threerod-shaped members are out of plane with the body member, and whereinthe at least three rod-shaped members extend from the same side of thebody member (that is, they have at least one directional component incommon).

In some embodiments, the body member has an opening therein. In someembodiments, at least two of the rod-shaped members are collinear. Forexample, in some embodiments, said at least three rod-shaped membersconsists of first, second, third, fourth, fifth, six, seventh, andeighth rod-shaped members. In some embodiments, the first and secondrod-shaped members are collinear, wherein the third and fourthrod-shaped members are collinear, wherein the fifth and sixth rod-shapedmembers are collinear, wherein the seventh and eighth rod-shaped membersare collinear, wherein the first and second rod-shaped members arecollinear, wherein the third and fourth rod-shaped members arecollinear, wherein the fifth and sixth rod-shaped members are collinear,wherein the seventh and eighth rod-shaped members are collinear, whereinthe first and third rod-shaped members are parallel, and wherein thefifth and seventh rod-shaped members are parallel. In some of theseembodiments, the first and fifth rod-shaped members are perpendicular toeach other.

And, in another aspect, methods of the present disclosure can be used toprovide shaped ceramic abrasive particles, wherein each of the shapedceramic abrasive particles has a body portion bounded by a peripheralloop portion having a roughened surface texture as compared to the bodyportion.

In another aspect, methods of the present disclosure can be used toprovide shaped ceramic precursor particles, wherein the shaped ceramicprecursor particles have a peripheral loop portion encircling andabutting an interior portion, and wherein the peripheral loop portioncomprises alpha alumina, and the interior portion comprises an alphaalumina precursor and is free of alpha alumina.

In another aspect, methods of the present disclosure can be used toprovide shaped ceramic abrasive particles, wherein the shaped ceramicabrasive particles have a peripheral loop portion encircling andabutting, but not fully enclosing, an interior portion, and wherein theperipheral loop portion has a different microcrystalline structure thanthe interior portion.

In another aspect, methods of the present disclosure can be used toprovide shaped ceramic precursor particles, wherein each of the shapedceramic precursor particles has first and second opposed nonadjacentmajor surfaces, a peripheral surface extending between the first andsecond major surfaces, wherein the peripheral surface comprises anablated region extending along the peripheral surface adjacent to thefirst major surface but not contacting the second major surface, and afractured region extending along the peripheral surface adjacent thesecond major surface but not contacting the first major surface.

In another aspect, methods of the present disclosure can be used toprovide shaped ceramic abrasive particles, wherein each of the shapedceramic abrasive particles has first and second opposed nonadjacentmajor surfaces, a peripheral surface extending between the first andsecond major surfaces, wherein the peripheral surface comprises anablated region extending along the peripheral surface adjacent to thefirst major surface but not contacting the second major surface, and afractured region extending along the peripheral surface adjacent thesecond major surface but not contacting the first major surface.

In another aspect, the present disclosure provides shaped ceramicabrasive particles, wherein each of the shaped ceramic abrasiveparticles comprises first and second opposed major surfaces that areconnected by first and second opposed sides and first and second opposedends, wherein the first and second opposed major surfaces aresubstantially smooth, wherein the first and second opposed sides and thefirst and second opposed ends have a surface topography comprisingtortuous rounded micrometer-scale projections and depressions, whereinthe first side abuts the first major surface forming an acute dihedralangle, and wherein the second side abuts the first major surface formingobtuse dihedral angle.

In some embodiments, shaped ceramic abrasive particles according to thepresent disclosure comprise alpha-alumina. In some embodiments, theshaped ceramic abrasive particles have a size distribution correspondingto an abrasives industry recognized nominal grade.

Advantageously, shaped ceramic abrasive particles according to thepresent disclosure may have compositional gradients, shapes, and/orstructures that have not been heretofore readily accessible, which mayresult in low packing density, increased particle to binder adhesion(for example, due to the texture on the abrasive particle surface),and/or abrading performance.

Accordingly, in yet another aspect, the present disclosure providesabrasive articles comprising shaped ceramic abrasive particles accordingto the present disclosure adhered with, or retained in, a binder (e.g.,as in a bonded abrasive article), or secured to a backing by a binder(e.g., as in a coated abrasive article).

As used herein:

the term “ablated region” refers to a region of a surface formed bymelting, evaporation, and/or vaporization (e.g., as caused by a laserbeam), generally characterized by an irregular topography comprisingrounded and/or sharp projections and smooth depressions;

the term “calcining” refers to heating to at least a temperature atwhich any remaining volatiles (including all organic materials andwater) that were present in a dried substrate are removed;

the term “drying” refers to removing at least some water contained inthe article being dried, but not necessarily all water;

the term “gravity” refers to gravitational force at the surface of theearth;

the term “micrometer-scale” refers to a size range of from 0.1micrometer to 1 millimeter;

the term “shaped particle” refers to a particle having a geometryresulting from a predetermined geometry used in making of the particle(for example, the geometry may be a result of molding in a cavity havinga predetermined precise geometry, or may be a result of a particularcutting pattern of by a cutting laser);

the term “sintering” refers to heating to at least a temperature atwhich chemical bonds form between contacting ceramic particles of acalcined substrate, typically resulting in increased strength anddensity; and

the term “substantially planar” means having a flat shape with arelatively broad surface in relation to thickness (for example, thethickness may be at least 2, 3, 4, 5, or even 10 times less than thelength and/or width of the surface).

In this application, it is intended that the open-ended term “comprise”also envisions embodiments wherein the term “comprise” is replaced bythe terms “consist essentially of” or “consist of.”

The foregoing aspects and embodiments may be implemented in anycombination thereof, unless such combination is clearly erroneous inview of the teachings of the present disclosure. The features andadvantages of the present disclosure will be further understood uponconsideration of the detailed description as well as the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a flow diagram of an exemplary method according to thepresent disclosure;

FIG. 1B is an enlarged schematic view of layer of ceramic precursormaterial 140 in FIG. 1A taken along line 1B;

FIG. 2A is a schematic top view of exemplary shaped ceramic precursorparticles 200 prepared according to a method of the present disclosure;

FIG. 2B is a schematic perspective view of an exemplary shaped ceramicabrasive particle 270 according to the present disclosure;

FIG. 3A is a schematic perspective view of an exemplary shaped ceramicprecursor particle 300 according to the present disclosure;

FIG. 3B is a schematic perspective view of an exemplary shaped ceramicabrasive particle 350 according to the present disclosure;

FIG. 4 is a scanning electron micrograph of an exemplary shaped ceramicabrasive particle 350.

FIG. 5A is a schematic perspective view of an exemplary shaped ceramicprecursor particle 500 according to the present disclosure;

FIG. 5B is a schematic perspective view of an exemplary shaped ceramicabrasive particle 550 according to the present disclosure

FIGS. 6A-6G are schematic perspective views of exemplary shaped ceramicabrasive particles according to the present disclosure;

FIG. 7A is a scanning electron micrograph of an exemplary shaped ceramicabrasive particle wherein the rod-shaped members are out of plane withthe body member;

FIG. 7B is an enlarged view of the exemplary shaped ceramic abrasiveparticle shown in FIG. 5A;

FIG. 8A is schematic perspective view of an exemplary shaped ceramicabrasive particle according to the present disclosure;

FIG. 8B is a scanning electron micrograph of an exemplary shaped ceramicabrasive particle according to the embodiment shown in FIG. 8A;

FIG. 9 is a perspective view of an exemplary bonded abrasive cut-offwheel 900 according to the present disclosure;

FIG. 10 is a side view of an exemplary coated abrasive article 1000according to the present disclosure;

FIG. 11 is a side view of an exemplary coated abrasive article 1100according to the present disclosure;

FIG. 12A is a perspective view of an exemplary nonwoven abrasive article1200 according to the present disclosure;

FIG. 12B is an enlarged view of region 12B in FIG. 12A;

FIGS. 13 and 14 are photomicrographs showing the result of laser cuttingthe layer of ceramic precursor material of Examples 1 and 2,respectively;

FIG. 15 is a scanning electron micrograph showing a shaped ceramicprecursor abrasive particle produced in Example 2;

FIG. 16 is a schematic plan view of the beam trace pattern used by thecutting laser in Example 4;

FIGS. 17A-17C are scanning electron micrographs of various particlesgenerated in Example 6; and

FIGS. 18A and 18B are scanning electron micrographs of a shaped ceramicabrasive particle prepared in Example 8.

While the above-identified drawing figures set forth several embodimentsof the present disclosure, other embodiments are also contemplated, asnoted in the discussion. In all cases, this disclosure presents thedisclosure by way of representation and not limitation. It should beunderstood that numerous other modifications and embodiments can bedevised by those skilled in the art, which fall within the scope andspirit of the principles of the disclosure. The figures may not be drawnto scale.

DETAILED DESCRIPTION

Referring now to FIG. 1A, in one exemplary method 100 according to thepresent disclosure, layer of ceramic precursor material 140 is supportedon carrier 190. As layer of ceramic precursor material 140 passes laserbeam 180, laser beam 180 forms cuts 184 (shown in FIG. 1B) through thelayer of ceramic precursor material 140 to form shaped ceramic precursorparticles 142, which are further dried by heater 150 and flexed bypassing over roller 195 resulting in separation from carrier 190 ofdried shaped ceramic precursor particles 144. The dried shaped ceramicprecursor particles 144 are optionally calcined to form calcined driedshaped ceramic precursor particles 146, optionally impregnated withinorganic salts, and sintered to provide shaped ceramic abrasiveparticles 160. While it is typical to dry shaped ceramic precursorparticles 142 to facilitate handling, it is not a requirement.Similarly, while it is typical to calcine the dried shaped ceramicprecursor particles 144, and impregnate the resultant calcined driedshaped ceramic precursor particles 146 with inorganic rare earth saltsto increase hardness prior to sintering, these are not requirements.

In embodiments wherein the laser only partially penetrates (e.g.,scores) the layer of ceramic precursor material 140, it forms latentshaped ceramic precursor particles which, after further drying andflexing by passing over roller 195, separate from one another as driedshaped ceramic precursor particles 144. While a roller is shown in theembodiment in FIG. 1A, it will be recognized that other methods may alsobe used such as, for example, beater bars or passing over a bar or knifeedge.

In the embodiment shown in FIGS. 1A and 1B, the layer of ceramicprecursor material 140, i.e., a material that when dried and sinteredforms a ceramic material (e.g., a boehmite sol-gel layer), is coatedonto carrier 190, although other methods may also be used. Typicalcoating processes are best-suited for materials with relatively lowerviscosity than the viscosity that is desirable for the laser cutting(that is, cutting with a laser beam) step. Accordingly, layer of ceramicprecursor material 140 is partially dried by heater 115 prior to thelaser cutting step.

In a variation of the process described in FIGS. 1A and 1B, the laserbeam does not cut through the layer of ceramic precursor material, butinstead only cuts partially through or forms perforations therebyforming score lines in the layer of ceramic precursor material to form ascored layer of ceramic precursor material, which is optionally furtherdried (for example, using a heater and/or oven), and then broken intodried shaped ceramic precursor particles along the score lines. Theresultant dried shaped ceramic precursor particles are then processed asdescribed in FIG. 1A to provide shaped ceramic abrasive particles.

The above exemplary processes will now be discussed in greater detail.

The first step involves coating, onto a carrier, a layer of ceramicprecursor material (e.g., as a seeded or un-seeded dispersion containingparticles of ceramic precursor) that can ultimately be converted intoceramic material. Examples of suitable ceramic precursors include: alphaalumina precursors such as aluminum oxide monohydrate (for example,boehmite); and zirconia precursors and mixed zirconia-alumina precursorssuch as those described in U.S. Pat. No. 5,551,963 (Larmie). Theparticles of ceramic precursor may be dispersed in (or mixed with) aliquid that comprises a volatile component that includes water, althoughthis is not a requirement. Dispersions and/or slurries preferablycomprise a sufficient amount of the liquid for the viscosity of thedispersion to be sufficiently low to enable a quality coating on thecarrier, but not so much liquid as to cause subsequent removal of theliquid dispersion to be prohibitively expensive. The dispersiontypically comprises from 30 to 50 percent by weight of ceramic precursorparticles and from 50 to 70 percent by weight of the volatile component,although other weight ratios may also be used. The physical propertiesof the resulting shaped ceramic abrasive particles will generally dependupon the type of material used in the dispersion.

Boehmite dispersions can be prepared by known techniques or can beobtained commercially. Examples of commercially available boehmiteinclude products having the trade designations “DISPERAL”, and “DISPAL”,both available from Sasol North America, Inc. and “HiQ-40” availablefrom BASF Corporation. These aluminum oxide monohydrates are relativelypure, that is, they include relatively little, if any, hydrate phasesother than monohydrates, and have a high surface area.

In one embodiment, the layer of ceramic precursor material (e.g.,dispersion of ceramic precursor particles) is in a gel state. As usedherein, a “gel” is a three-dimensional network of solids dispersed in aliquid. The dispersion may contain a modifying additive or precursor ofa modifying additive. The modifying additive can function to enhance oneor more desirable properties of the shaped ceramic abrasive particles orincrease the effectiveness of the subsequent sintering step. Modifyingadditives or precursors of modifying additives can be in the form ofsoluble salts, typically water-soluble salts. They typically include ametal-containing compound and can be a precursor of oxide of magnesium,zinc, iron, silicon, cobalt, nickel, zirconium, hafnium, chromium,yttrium, praseodymium, samarium, ytterbium, neodymium, lanthanum,gadolinium, cerium, dysprosium, erbium, titanium, and mixtures thereof.The particular concentrations of these additives that can be present inthe dispersion can be varied based on skill in the art. Typically, theintroduction of a modifying additive or precursor of a modifyingadditive will cause the dispersion to gel. The dispersion can also beinduced to gel by application of heat over a period of time.

The dispersion of ceramic precursor particles can also contain anucleating agent to enhance the transformation of hydrated or calcinedaluminum oxide to alpha alumina. Nucleating agents suitable for thisdisclosure include fine particles of alpha alumina, alpha ferric oxideor its precursor, titanium oxides and titanates, chrome oxides, or anyother material that will nucleate the transformation. The amount ofnucleating agent, if used, should be sufficient to effect thetransformation of alpha alumina. Nucleating such dispersions isdisclosed in U.S. Pat. No. 4,744,802 (Schwabel).

A peptizing agent can be added to dispersion of ceramic precursorparticles to produce a more stable hydrosol or colloidal dispersion.Suitable peptizing agents include monoprotic acids or acid compoundssuch as acetic acid, hydrochloric acid, formic acid, and nitric acid.Multiprotic acids can also be used but they can rapidly gel the abrasivedispersion, making it difficult to handle or to introduce additionalcomponents thereto. Some commercial sources of boehmite contain an acidtiter (such as absorbed formic or nitric acid) that will assist informing a stable abrasive dispersion.

The dispersion of ceramic precursor particles can be created or formedby any suitable means, such as, for example, simply by mixing aluminumoxide monohydrate with water containing a peptizing agent or by formingan aluminum oxide monohydrate slurry to which the peptizing agent isadded. Defoamers or other suitable chemicals can be added to reduce thetendency to form bubbles or entrain air while mixing. Additionalchemicals such as wetting agents, alcohols, or coupling agents can beadded if desired.

Additional additives useful for dispersions of alpha-alumina ceramicprecursor materials include: silica and iron oxide as disclosed in U.S.Pat. No. 5,645,619 (Erickson et al.); zirconia as disclosed in U.S. Pat.No. 5,551,963 (Larmie); and nucleating agents as disclosed in U.S. Pat.No. 6,277,161 (Castro).

Coating of a dispersion of ceramic precursor material to form the layerof ceramic precursor material may be accomplished by any suitable methodincluding, for example, knife coating, bar coating, slot die coating,curtain coating, gravure coating, or roll coating. The carrier istypically a thin readily handleable substrate such as a paper, film,foil, belt, although other substrates may be used if desired. Thecarrier may be selected to releasably adhere to the shaped ceramicprecursor particles, but this is not a requirement; for example, inthose cases in which the substrate is cut through during the lasercutting operation and subsequently burned off during calcining Examplesof suitable carriers include papers (for example, including siliconizedpaper or waxed paper), polymer films (for example, polypropylene, orpolyester film), and metal belts (for example, stainless steel belts).The carrier may be treated with a release agent (e.g., a fluorochemical,peanut oil, or silicone) prior to use, if desired.

Second, after coating, the dispersion of ceramic precursor material isoptionally partially dried an amount sufficient to render the layer ofceramic precursor material non-flowable under action of gravity alone(for example, over a span of 5 to 20 minutes). This helps to preventsagging or slumping of the shaped ceramic precursor particles afterlaser cutting until they can be further processed. If appropriatelydried, the layer of ceramic precursor material is typicallysubstantially free of cracks caused by drying the sol-gel layer.However, excessive drying can lead to undesirable cracking of the layerof ceramic precursor material. For alpha-alumina ceramic precursormaterials, a solids content after partial drying of from 40 to 75percent by weight, and more typically 60 to 70 percent by weight, areparticularly useful. Suitable devices for partially drying the coateddispersion include heaters (for example, infrared heaters, heat guns,radiated heat from below through the carrier and/or microwave lamps),ovens, hot cans, superheated steam, and forced air.

Third, the layer of ceramic precursor material is cut so as to formshaped ceramic precursor particles. The laser used for cutting the layerof ceramic precursor material may be any suitable laser operating at aninfrared, visible, and/or ultraviolet output wavelength. Examples ofsuitable lasers include gas lasers, excimer lasers, solid state lasers,and chemical lasers. Exemplary gas lasers include: carbon dioxide lasers(for example, those which produce power up to 100 kW at 10.6 μm);argon-ion lasers (for example, those which emit light at 458 nanometers(nm), 488 nm or 514.5 nm); carbon-monoxide lasers (for example, thosewhich can produce power of up to 500 kW); and metal ion lasers, whichare gas lasers that generate deep ultraviolet wavelengths. Helium-silver(HeAg) 224 nm lasers and neon-copper (NeCu) 248 nm lasers are twoexamples. These lasers have particularly narrow oscillation linewidthsof less than 3 GHz (0.5 picometers). CO₂ lasers are typicallywell-suited for practice of the present disclosure.

Chemical lasers are powered by a chemical reaction, and can achieve highpowers in continuous operation. For example, in the hydrogen fluoridelaser (2700-2900 nm) and the deuterium fluoride laser (3800 nm), thereaction is the combination of hydrogen or deuterium gas with combustionproducts of ethylene in nitrogen trifluoride.

Excimer lasers are powered by a chemical reaction involving an exciteddimer (that is, an “excimer”) which is a short-lived dimeric orheterodimeric molecule formed from two species (atoms), at least one ofwhich is in an excited electronic state. They typically produceultraviolet light. Commonly used excimer molecules include F2 (fluorine,emitting at 157 nm), and noble gas compounds (ArF (193 nm), KrCl (222nm), KrF (248 nm), XeCl (308 nm), and XeF (351 nm)).

Solid state laser materials are commonly made by doping a crystallinesolid host with ions that provide the required energy states. Examplesinclude ruby lasers (for example, made from ruby or chromium-dopedsapphire). Another common type is made from neodymium-doped yttriumaluminum garnet (YAG), known as Nd:YAG. Nd:YAG lasers can produce highpowers in the infrared spectrum at 1064 nm. Nd:YAG lasers are alsocommonly frequency doubled to produce 532 nm when a visible (green)coherent source is desired.

Ytterbium, holmium, thulium, and erbium are other common dopants insolid state lasers. Ytterbium is used in crystals such as Yb:YAG,Yb:KGW, Yb:KYW, Yb:SYS, Yb:BOYS, Yb:CaF₂, typically operating around1020-1050 nm. They are potentially very efficient and high powered dueto a small quantum defect. Extremely high powers in ultrashort pulsescan be achieved with Yb:YAG. Holmium-doped YAG crystals emit at 2097nanometers (nm) and form an efficient laser operating at infraredwavelengths strongly absorbed by water-bearing tissues. The Ho-YAG isusually operated in a pulsed mode. Titanium-doped sapphire (Ti:sapphire)produces a highly tunable infrared laser, commonly used for spectroscopyas well as the most common ultrashort pulsed laser. Solid state lasersalso include glass or optical fiber hosted lasers, for example, witherbium or ytterbium ions as the active species. Fiber lasers (e.g.,infrared fiber lasers) are one exemplary type of solid state lasersuitable for practicing the present disclosure. Fiber lasers have afiber core (typically having a diameter in a range from 0.1 micrometer(μm)-1000 μm) that is the lasing media.

The laser may be used in pulsed and/or continuous wave mode. Forexample, the laser may operate at least partially in continuous wavemode and/or at least partially in pulsed mode. Individual pulses may betemporally profiled. One specific example of a suitable pulse laser is aCO₂ laser, model Diamond 84, available from Coherent, Inc. of SantaClara, Calif., which has the following technical specifications: RFexcited, sealed CO₂ pulsed laser, scanner-based, input beam diameter=7.0millimeters (mm), and final beam diameter=0.250 mm; operatingwavelength=10.6 μm; max power at 60 percent duty cycle at one kilohertz(kHz)=300 W; pulse energy range=10-450 millijoules (mJ); pulse widthrange=10-1000 microseconds (μS); and pulse rise and fall time<60 μS.

One specific example of a suitable continuous wave laser is a CO₂ laser,Evolution series, available from Synrad of Mukilteo, W. Va., which hasthe following technical specifications: Wavelength: 10.6 μm; Max power:−Continuous Mode: 100 watts (W), −Pulsed Mode: 150 W; Modulation: Up to20 kHz; Rise Time: <150 μS; Description: RF excited, sealed CO₂ Pulsedlaser to CW output; Method of Delivery: XY Plotter based; Input beamdiameter: 4.0 mm; Final beam diameter: 0.250 mm.

In those embodiments in which an aluminum-based aqueous sol-gelcomprises the layer of ceramic precursor material a CO₂ laser tuned to awavelength of 9.37 micrometers may be particularly useful.

The effectiveness of laser cutting is highly sensitive to the degree towhich the laser beam is absorbed by medium (e.g., layer of ceramicprecursor material) being cut. At some ultraviolet wavelengths (e.g.,UV-B or UV-C wavelengths), absorption may be appreciable, however, atlonger wavelengths absorption typically become more problematic, and itis preferred that the wavelength of the laser beam is either tuned to aspecific absorption of the layer of ceramic precursor material or anabsorber (i.e., a material that is highly absorptive at the laserwavelengths) is added to the ceramic precursor. The role of absorbers isto absorb electromagnetic radiation of the laser beam and convert it toheat. Suitable absorbers preferably have absorption bands in theultraviolet, visible, and/or infrared portions of the electromagneticspectrum. In general, the absorber should have a high molar extinctioncoefficient as the wavelengths of the laser beam. Preferably, theabsorber has a molar extinction coefficient at of least 1,000 (moles perliter)⁻¹-centimeter⁻¹ (M⁻¹cm⁻¹), 500 M⁻¹cm⁻¹, 10,000 M⁻¹cm⁻¹ or even atleast 25000 M⁻¹cm⁻¹ at the principal wavelength of the laser beam.Combinations of absorbers can also be used. If present, absorber(s) arepreferably present in sufficient amount to absorb at least 5, 10, 20,30, 40, 50, 60, 70, or even at least 80 percent of the incidentelectromagnetic radiation of the laser beam. Quantities used will varydepending on the absorbance spectrum of the absorber(s), thewavelength(s) of the laser beam, and the thickness of the layer ofsol-gel ceramic precursor and may be readily determined, for example,according to the Beer-Lambert Law.

Typically, a focused laser spot size is limited to a spot size of about10 times the laser wavelength. So for UV lasers, the laser spot can befocused to a diameter of less than 10 micrometers. However, for infraredlasers, the focused spot diameter is typically on the order of from 100to 250 micrometers, although this is not a requirement. In someembodiments, the ultimately produced shaped ceramic abrasive particleswill have sharp edges and corners; preferably having a radius ofcurvature of less than or equal to 6 micrometers. Achieving small cornerradius of curvature may be difficult with larger spot sizes. Forexample, it is difficult to use a laser beam with a 250 micrometers widespot diameter to draw a corner less that is than 10 micrometers inradius.

Suitable absorbers include dyes and pigments (preferably with at leastsome water-solubility) such as, for example, phthalazines, cyanines,pyryliums, luminols, Naphthol Green B (acid Green 1), Indocyanine green,naphthoquinones, anthraquinones, tetrakis amminium compounds, metalthiolenes, sulfonated or carboxylated metal phthalocyanines, and carbonblack. Examples of commercially available near infrared dyes includethose available as: TETRAARYLDIAMINE, product code FHI 104422P, fromFabric Color Holding Company, Paterson, N.J.; LUNIR5 NIR absorbingpigment and LUWSIR-3 Water Soluble NIR Absorber from Lumichem, Budapest,Hungary; and EPOLIGHT 2735 NEAR INFRARED DYE from Epolin, Inc. Newark,N.J. Preferably, the absorber(s) have at least some solubility ordispersibility in water, although this is not a requirement. In order toincrease water-dispersibility, absorber(s) may be used in combinationwith a surfactant and/or dispersant to facilitate incorporation into thelayer of ceramic precursor material.

While not required, it is preferable that the carrier supporting thelayer of ceramic precursor material not be highly absorptive of thelaser beam in order to minimize damage of the carrier. This can beachieved, for example, by laser selection, carrier selection, inclusionof absorber(s) in the layer of ceramic precursor material, or acombination thereof. For example, typical boehmite sol-gels have anabsorption maximum at about 9.4 micrometers, a wavelength at whichabsorption by polyethylene terephthalate (PET) polyester is minimal. Insuch a case a laser with a wavelength of about 9.4 micrometers ispreferably used. Accordingly, it is desirable to choose a laser with awavelength that is highly absorbed by layer of ceramic precursormaterial such that little laser radiation reaches the carrier.

The laser beam is typically optically directed or scanned and modulatedto form a desired cutting pattern that achieves the desired shapedceramic abrasive particle shape. The laser beam may be directed througha combination of one or more mirrors (for example, rotating mirrorsand/or scanning mirrors) and/or lenses. Alternatively or in addition,the substrate can be moved relative to the laser beam. In yet anotherconfiguration, the focusing element can move relative to the web (e.g.,one or more of X, Y, Z alpha, or theta directions). The laser beam maybe scanned at an angle of incidence relative to the surface (e.g., uppersurface) of the layer of ceramic precursor material. For example, theangle of incidence may be 90° (i.e., perpendicular to the layer ofceramic precursor material), 85°, 83°, 80°, 70°, 60°, 50°, 45° or evenless.

Typically, the cutting pattern is generated such that a high packingdensity (for example, a maximum packing density) of the resulting shapedceramic precursor particles is achieved. For example, the pattern maycut the layer of ceramic precursor material into a close-packed array ofshapes such as triangles, squares, rectangles, or hexagons.

FIG. 2A shows an exemplary array 200 of shaped ceramic precursorparticles 210. Under at least some laser cutting conditions (forexample, those conditions in which the laser beam has cut substantiallyor completely through the layer of ceramic precursor material), heatingthat occurs along the cut lines 230 may result in flash evaporation ofwater in the sol-gel thereby forming a porous surface texture, whichthen remains immobilized (that is, “frozen in place”) throughoutsubsequent processing steps. Accordingly, shaped ceramic precursorparticles 210 may, in some embodiments, have a body portion 237 boundedby a peripheral loop portion 235 having a roughened surface texture ascompared to the surface texture of body portion 237, while in otherembodiments a smooth surface along cut lines can be observed after lasercutting. Calcining and sintering shaped ceramic precursor particles 210results in shaped ceramic abrasive particles 270 (see FIG. 2B, whereinsurface texture of the shaped ceramic precursor particles 210 carriesthrough to shaped ceramic abrasive particles 270. Hence, shaped ceramicabrasive particles 270 (shown in FIG. 2B) may, in some embodiments, havea body portion 277 bounded by a peripheral loop portion 275 having aroughened surface texture as compared to the body portion 277 (forexample, as shown in FIGS. 7A and 7B). The roughened surface texture mayfacilitate electrostatic coating and/or adhesion to binder resin (forexample, in a make coat or slurry coat).

In some embodiments, the laser cuts penetrate through the layer ofceramic precursor material. In some embodiments, the laser does notpenetrate through the layer of ceramic precursor material, but cutsscore lines along which the shaped ceramic precursor particles can beobtained, generally after further drying, by breaking the layer ofceramic precursor material along the score lines. Breakage may beaccomplished, for example, by ultrasonic vibration, beater bars,rollers, scrapers, and combinations thereof.

While not a requirement, for efficiency the layer of ceramic precursormaterial is scored by the laser beam such that it forms a close-packedarray of latent abrasive precursor particles, which if the laser beamcuts completely through the layer of ceramic precursor material areseparated but adjacent to one another, or, if the laser beam cuts onlypartially through the layer of ceramic precursor material, which arejoined to one another along score lines formed by the laser beam in thelayer of ceramic precursor material.

In embodiments in which the laser beam cuts completely through the layerof ceramic precursor material, subsequent drying and deformation (e.g.,flexing as carrier 190 travels around roller 195 as shown in FIG. 1A)leads to separation of the shaped ceramic precursor particles from thecarrier.

In embodiments in which the laser beam cuts only partially through thelayer of ceramic precursor material, subsequent drying and deformation(e.g., flexing as carrier 190 travels around roller 195 as shown in FIG.1A) causes cracks to form along the score lines, thereby facilitatingseparation of the shaped ceramic precursor particles from one anotherand the carrier. For best results, the layer of ceramic precursormaterial should be allowed to dry a point where cracks (e.g., similar inappearance to mud cracks) begin to form at peripheral regions of thelayer.

Shaped ceramic precursor particles formed in this manner may becharacterized by peripheral surfaces with dual characteristics: aportion formed by evaporation/ablation of precursor ceramic material,and a portion formed by fracture of the layer after at least partialdrying as shown in FIG. 3A. Referring now to FIG. 3A, shaped ceramicprecursor particle 300 has first and second opposed nonadjacent majorsurfaces 312, 314 and peripheral surface 320 extending between first andsecond major surfaces 312, 314. Peripheral surface 320 comprises anablated region 324 extending along peripheral surface 320 adjacent tofirst major surface 312, but not contacting second major surface 314.Fractured region 326 extends along peripheral surface 320 adjacent thesecond major surface, but does not contact first major surface 312.

Upon conversion of the shaped ceramic precursor particles shown in FIG.3A to shaped ceramic abrasive particles (shown in FIG. 3B), for example,by sintering, the resultant shaped ceramic abrasive particles 350.Referring now to FIG. 3B, shaped ceramic abrasive particle 350 has firstand second opposed nonadjacent major surfaces 362, 364 and peripheralsurface 370 extending between first and second major surfaces 362, 364.Peripheral surface 370 comprises an ablated region 374 extending alongperipheral surface 370 adjacent to first major surface 362, but notcontacting second major surface 364. Fractured region 376 extends alongperipheral surface 320 adjacent the second major surface, but does notcontact first major surface 312. As shown, ablated region 374 andfractured region 376 abut one another and comprise the entire area ofthe peripheral surface, although this is not a requirement. For furtherreference, a photomicrograph of an exemplary shaped ceramic precursorparticle according to this embodiment is shown in FIG. 4. Depending onthe depth of the score lines used to form the shaped ceramic precursorparticles, either of the fractured region or the ablated region maycomprise a majority of the area of the peripheral surface. To facilitaterapid processing, it is preferred that the depth of the score lines isminimized, leading to a relatively larger fractured region.

When using the laser to form score lines that only partially penetratethe layer of ceramic precursor material, in some cases, undesirablecracks not corresponding to the score lines may form as well. Tominimize this effect, it may be desirable to use the laser beam todivide the layer of ceramic precursor material into multiple regionsbounded by a line that extends completely through the layer of ceramicprecursor material. This boundary line (which may have any width, but itpreferably the width of a single laser scan line), serves to interruptthe propagation of any extraneous crack that may form in a portion ofthe layer of ceramic precursor material, thereby reducing waste.Accordingly, in some embodiments, boundary lines are formed in the layerof ceramic precursor material (e.g., surrounding or within aclose-packed array of latent dried ceramic precursor particles) bycutting through the layer of ceramic precursor material using the laserbeam, such that the boundary lines separate portions of the close-packedarray of latent dried ceramic precursor particles.

In some embodiments, the shaped ceramic abrasive particles comprise thinbodies having opposed major surfaces connected by at least one sidewalland separated by a thickness. In some embodiments, the thickness rangesbetween about 25 micrometers to about 500 micrometers. Typically,increasing thicknesses are associated with increasing dwell times for agiven laser in order to achieve a useful level of cutting.

Advantageously, under some circumstances (e.g., wherein high laser poweris used), extreme heating caused by the laser beam can result inconversion of the ceramic precursor material into ceramic adjacent cutsmade by the laser beam. In the case of boehmite gel, this means thatalpha alumina is formed at peripheral surfaces of the shaped ceramicprecursor particles, while an interior portion of the particles remainsin a precursor (e.g., at least partially dried boehmite sol-gel).Accordingly, methods according to the present disclosure can produceshaped ceramic precursor particles of the Type shown in FIG. 5A, whereina shaped ceramic precursor particle 500 has a peripheral loop portion510 encircling and abutting an interior portion 520. Peripheral loopportion 510 (e.g., see FIG. 18B) has a different microcrystallinestructure than interior portion 520 (e.g., see FIG. 18A).

Upon conversion of the shaped ceramic precursor particles shown in FIG.5A to shaped ceramic abrasive particles (shown in FIG. 5B), for example,by sintering, the resultant shaped ceramic abrasive particles 550 have aperipheral loop portion 560 encircling and abutting an interior portion570. Alpha alumina in the shaped ceramic precursor particles, peripheralloop portion 560 serves to control the formation of ceramicmicrocrystalline grains (e.g., alpha alumina microcrystalline grains) inthe shaped ceramic abrasive particles, resulting in differences inmicrocrystalline structure between the peripheral loop portion and theinterior portion.

Additionally, by using laser cutting processes according to the presentdisclosure, it is possible to easily make shaped ceramic abrasiveparticles with shapes that are not possible using conventional openmolds due to shrinkage and/or cracking upon drying in the mold. Examplesof such shapes include shaped ceramic abrasive particles that comprise abody member and at least three rod-shaped members extending from thebody member. The rod shaped members may have any cross-sectionalprofile. For example, they may have cross-sectional profilesindependently selected from a circle, an ellipse, a square, a rectangle,or a triangle. Unexpectedly, the present inventors have discovered thatunder some circumstances the rod-shaped members curl away from thecarrier during the laser cutting operation. The degree of curl istypically influenced by humidity conditions during drying. More humidconditions during drying tend to reduce observed curl. In such cases,the at least three rod-shaped members are out of plane with the respectto the body member, and extend from the same side of the body member.This leads to shaped ceramic abrasive particles that have a low bulkpacking density. For example, the shaped ceramic abrasive particles mayhave a bulk packing density of from 20 percent to 90 percent of thetheoretical maximum, from 20 percent to 60 percent of the theoreticalmaximum, or from 20 percent to 40 percent of the theoretical maximum.

Shaped ceramic abrasive particle shapes wherein shrinkage in an openmold would lead to cracking and/or breaking include, for example,lambda, cross-hatch, T, Y, or tic-tac-toe patterns. Exemplary suchshapes are shown in FIGS. 6A-6G.

For example, FIG. 6A shows a substantially planar shaped ceramicabrasive particle 600A comprising a body member 670A and four rod-shapedmembers 681A, 682A, 683A, and 684A extending from body member 670A,forming the shape of a cross. The ends of rod-shaped members may besquared off, substantially squared off as in end 691A, rounded as in end692A, tapered, or some other shape, or the ends may collectivelycomprise mixture of the foregoing shapes.

FIG. 6B shows a substantially planar shaped ceramic abrasive particle600B comprising a body member 670B and three rod-shaped members 681B,682B, and 683B extending from body member 670B, forming the shape of theletter T. In this embodiment, rod-shaped members 681B and 682B arecollinear.

FIG. 6C shows a substantially planar shaped ceramic abrasive particle600C comprising a body member 670C and six rod-shaped members 681C,682C, 683C, 684C, 685C, and 686C extending from body member 670C,forming the shape of a star or an asterisk. In this embodiment,respective rod-shaped members 681C and 682C, 683C and 684C, and 685C and686C are collinear.

FIG. 6D shows a substantially planar shaped ceramic abrasive particle600D comprising a body member 670D and three rod-shaped members 681D,682D, and 683D extending from body member 670D, forming the shape of theGreek letter lambda. In this embodiment, rod-shaped members 681D and682D are collinear.

In some embodiments, the shaped ceramic abrasive particles may be shapedsuch that the first and second rod-shaped members are collinear, thethird and fourth rod-shaped members are collinear, the fifth and sixthrod-shaped members are collinear, the seventh and eighth rod-shapedmembers are collinear, the first and second rod-shaped members arecollinear, the third and fourth rod-shaped members are collinear, thefifth and sixth rod-shaped members are collinear, the seventh and eighthrod-shaped members are collinear, the first and third rod-shaped membersare parallel, and the fifth and seventh rod-shaped members are parallel.In some of these embodiments, the first and fifth rod-shaped members areperpendicular to each other.

FIG. 6E shows a substantially planar shaped ceramic abrasive particle600E comprising a body member 670E and eight rod-shaped members 681E,682E, 683E, 684E, 685E, 686E, 687E, and 688E extending from body member670E, which has an opening 665E therein. Rod-shaped members 681E and682E, 683E and 684E, 685E and 686E, and 687E and 688E are collinear.Rod-shaped members 681E and 685E are perpendicular to each other,forming the shape of a tic-tac-toe grid. In this case, body member 670Ehas the shape of a hollow square.

Similarly, FIG. 6F shows a substantially planar shaped ceramic abrasiveparticle 600F comprising a body member 670F and eight rod-shaped members681F, 682F, 683F, 684F, 685F, 686F, 687F, and 688F extending from bodymember 670F. Rod-shaped members 681F and 682F, 683F and 684F, 685F and686F, and 687F and 688F are collinear. Rod-shaped members 681F and 685Fare perpendicular to each other, forming the shape of a filled intic-tac-toe grid. In this case, body member 670F has the shape of afilled-in square.

Likewise, FIG. 6G shows a substantially planar shaped ceramic abrasiveparticle 600G comprising a body member 670G and eight rod-shaped members681G, 682G, 683G, 684G, 685G, 686G, 687G, and 688G extending from bodymember 670G, which has an opening 665G therein. Rod-shaped members 681Gand 682G, 683G and 684G, 685G and 686G, and 687G and 688G are collinear.Rod-shaped members 681G and 685G are perpendicular to each other,forming a tic-tac-toe-type grid having a circular central openingcentrally located in body member 670G.

Unexpectedly, the inventors have presently discovered that using laserprocessing techniques as described herein, it is possible to generateshaped ceramic abrasive particles wherein rod-shaped members extend froma body member and curl away from the carrier substrate during lasercutting, resulting in a shape wherein the rod-shaped members are out ofplane with the respect to the body member, and extend from the same sideof the body member. Such curling/bending of the rod-shaped members mayresult from differential shrinkage and/or decomposition of the carriersubstrate during laser processing. An exemplary such shaped ceramicabrasive particle, produced according to Example 4 is shown in FIGS. 7Aand 7B.

In another embodiment, methods according to the present disclosure areuseful for preparing elongate shaped ceramic abrasive particles noteasily preparable by other methods such as extrusion and molding.Referring now to FIG. 8A, exemplary shaped ceramic abrasive particle 800comprises first and second opposed major surfaces 810, 812 that areconnected by first and second opposed sides 820, 822 and first andsecond opposed ends 830, 832. First and second opposed major surfaces810, 812 are substantially smooth (as used herein the term“substantially smooth” means generally smooth, but which may containminor amounts of surface roughness, e.g., as resulting fromimperfections and irregularities during preparation). First and secondopposed sides 820, 822 and first and second opposed ends 830, 832 have asurface topography comprising tortuous rounded micrometer-scaleprojections 840 and depressions 850. In some embodiments, the surfacetopography consists of the tortuous rounded micrometer-scale projectionsand depressions, while in other embodiments the tortuous roundedmicrometer-scale projections and depressions cover only a portion of thefirst and second opposed sides and first and second opposed ends. In theembodiment shown in FIG. 8A, the first side 820 abuts first majorsurface 810 forming an acute dihedral angle 870. Second side 822 abutsfirst major surface 810 forming obtuse dihedral angle 872. FIG. 18 showsan exemplary such shaped ceramic abrasive particle prepared according toExample 7. Preferably, the first and second opposed ends comprisesparallel parallelograms. Preferably, the first and second opposed sidesare substantially parallel.

While the foregoing shaped ceramic abrasive particles can be madeaccording a laser cutting process according to the present disclosure,they may also be made by other techniques such as, for example,microextrusion of sol-gel ceramic precursor material. In suchembodiments, the rod-shaped members may cross over one another wherethey meet and form the body member, and/or they may meet flush with thebody member.

If desired, the cutting pattern may generate multiple shapes of ceramicprecursor particles, which may be left in a combined state or which maybe separated by shape (for example, by sieving). In some embodiments,the laser may be directed at the layer of ceramic precursor materialsuch that cuts are substantially perpendicular to its exposed surface.In some embodiments, the laser may be directed at the layer of ceramicprecursor material such that cuts are substantially at an angle relativeto its exposed surface.

Typically, the laser beam has a profile wherein power is concentrated incertain portions (for example, the beam center), although this is notnecessarily a requirement, or even desirable. As a consequence, thelaser cuts may resemble valleys with sloping sidewalls. In otherembodiments, the beam may have a flattened, e.g., to produceperpendicular walls.

Once formed, the shaped ceramic precursor particles are optionallyfurther dried, for example, using drying techniques as describedhereinabove, prior to separating them from the carrier. The purpose ofadditional drying at this stage is to increase the durability of theparticles and reduce the chances of cracking and/or breakage duringsubsequent processing. For example, the shaped ceramic precursorparticles may be dried from 1 to 480 minutes, or from 120 to 400minutes, at a temperature in a range of from 50° C. to 160° C. or at120° C. to 150° C.

The shaped ceramic precursor particles are typically separated from thecarrier prior to subsequent process steps that may include, for example,calcining, metal ion doping, and sintering. In some cases, for example,those cases in which the carrier is combustible, it may be possible tofurther process the carrier with shaped ceramic precursor particlesstill on it as it will be burned off during calcining or sintering.Methods such as, for example, vibration (including ultrasonicvibration), scraping, vacuum, or pressurized air may be useful tofacilitate the separation. In some cases, the shaped ceramic precursorparticles may spontaneously separate; for example, while passing arounda roll.

The next step typically involves calcining the shaped ceramic precursorabrasive particles. During calcining, essentially all volatile materialis removed, and various components that were present in the abrasivedispersion are transformed into metal oxides. During calcining, theshaped ceramic precursor abrasive particles are generally heated to atemperature of from 400° C. to 800° C., and maintained within thistemperature range until the free water and over 90 percent by weight ofany bound volatile material are removed.

In an optional next step, it may be desired to introduce a modifyingadditive such as an additive metal by an impregnation process. Forexample, a metal oxide additive, or a precursor thereof such as asoluble metal salt, can be introduced by impregnation into the pores ofthe calcined shaped ceramic precursor particles. Then, the impregnatedparticles are pre-fired again. This option is further described in U.S.Pat. No. 5,164,348 (Wood). Examples of additive metals includezirconium, magnesium, hafnium, cobalt, nickel, zinc, yttrium,praseodymium, samarium, ytterbium, neodymium, lanthanum, gadolinium,cerium, dysprosium, and erbium. The preferred modifying additive is anoxide of yttrium, magnesium, and a rare earth metal selected frompraseodymium, samarium, ytterbium, neodymium, lanthanum, gadolinium,cerium, dysprosium, and erbium.

The last step in making shaped ceramic abrasive particles involvessintering the calcined, optionally impregnated, shaped ceramic precursorparticles. Prior to sintering, the calcined shaped ceramic precursorparticles are not completely densified, and thus lack the hardness to beused as abrasive particles. Sintering takes place by heating thecalcined shaped ceramic precursor particles to a temperature of from1000° C. to 1650° C. and maintaining them within this temperature rangeuntil substantially all of the ceramic precursor is converted toceramic.

In the case of alumina monohydrate (or its equivalent) sinteringconverts to it to alpha-alumina and the porosity is reduced to less than15 percent by volume. The length of time to which the calcined shapedceramic precursor particles must be exposed to the sintering temperatureto achieve a sufficient level of conversion depends upon variousfactors, but usually from five seconds to 48 hours is typical (forexample, in the case of alpha-alumina). In one embodiment, the durationfor the sintering step ranges from one minute to 90 minutes. Oncesintered, the resultant shaped ceramic abrasive particles can have aVickers hardness of 10 gigapascals (GPa), 16 GPa, 18 GPa, 20 GPa, orgreater.

Other steps can be used to modify the described process, such as rapidlyheating the material from the calcining temperature to the sinteringtemperature, centrifuging the dispersion of ceramic precursor particlesto remove sludge, waste, and other solid particulates. Moreover, theprocess can be modified by combining two or more of the process steps ifdesired. Conventional process steps that can be used to modify theprocess of this disclosure are more fully described in U.S. Pat. No.4,314,827 (Leitheiser).

The shaped ceramic abrasive particles may also have a surface coating.Surface coatings are known to improve the adhesion between abrasivegrains and the binder in abrasive articles or can be used to aid inelectrostatic deposition of the shaped ceramic abrasive particles. Suchsurface coatings are described, for example, in U.S. Pat. No. 1,910,444(Nicholson); U.S. Pat. No. 3,041,156 (Rowse et al.); U.S. Pat. No.4,997,461 (Markhoff-Matheny et al.); U.S. Pat. No. 5,009,675 (Kunz etal.); U.S. Pat. No. 5,011,508 (Wald et al.); U.S. Pat. No. 5,042,991(Kunz et al.); U.S. Pat. No. 5,085,671 (Martin et al.); and U.S. Pat.No. 5,213,591 (Celikkaya et al.). Additionally, the surface coating mayprevent the shaped ceramic abrasive particle from capping. Capping isthe term to describe the phenomenon where metal particles from theworkpiece being abraded become welded to the tops of the shaped ceramicabrasive particles. Surface coatings to perform the above functions areknown to those of skill in the art.

Shaped ceramic abrasive particles made according to the presentdisclosure can be incorporated into an abrasive article, or used inloose form. Abrasive particles are generally graded to a given particlesize distribution before use. Such distributions typically have a rangeof particle sizes, from coarse particles to fine particles. In theabrasive art this range is sometimes referred to as a “coarse”,“control”, and “fine” fractions. Abrasive particles graded according toabrasive industry accepted grading standards specify the particle sizedistribution for each nominal grade within numerical limits. Suchindustry accepted grading standards (that is, abrasive industryspecified nominal grade) include those known as the American NationalStandards Institute, Inc. (ANSI) standards, Federation of EuropeanProducers of Abrasive Products (FEPA) standards, and Japanese IndustrialStandard (JIS) standards. As used herein, the term “nominal” means: of,being, or relating to a designated or theoretical size and/or shape thatmay vary from the actual.

ANSI grade designations (that is, specified nominal grades) include:ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 40, ANSI 50,ANSI 60, ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600. FEPA gradedesignations include P8, P12, P16, P24, P36, P40, P50, P60, P80, P100,P120, P150, P180, P220, P320, P400, P500, P600, P800, P1000, and P1200.JIS grade designations include JIS8, JIS12, JIS16, JIS24, JIS36, JIS46,JIS54, JIS60, JIS80, JIS100, JIS150, JIS180, JIS220, JIS240, JIS280,JIS320, JIS360, JIS400, JIS600, JIS800, JIS 1000, JIS 1500, JIS2500,JIS4000, JIS6000, JIS8000, and JIS10,000.

Alternatively, the shaped ceramic abrasive particles can graded to anominal screened grade using U.S.A. Standard Test Sieves conforming toASTM E-11 “Standard Specification for Wire Cloth and Sieves for TestingPurposes.” ASTM E-11 prescribes the requirements for the design andconstruction of testing sieves using a medium of woven wire clothmounted in a frame for the classification of materials according to adesignated particle size. A typical designation may be represented as−18+20 meaning that the shaped ceramic abrasive particles pass through atest sieve meeting ASTM E-11 specifications for the number 18 sieve andare retained on a test sieve meeting ASTM E-11 specifications for thenumber 20 sieve. For example, the shaped ceramic abrasive particles mayhave a nominal screened grade of: −18+20, −20+25, −25+30, −30+35,−35+40, −40+45, −45+50, −50+60, −60+70, −70+80, −80+100, −100+120,−120+140, −140+170, −170+200, −200+230, −230+270, −270+325, −325+400,−400+450, −450+500, or −500+635.

If desired, the shaped ceramic abrasive particles and/or shaped ceramicprecursor particles may be selected on the basis on non-standard sizegrades. For example, the shaped ceramic abrasive particles and/or shapedceramic precursor particles may be selected to have a length (i.e.,maximum dimension) in a range of from 0.001 micrometer to 26micrometers, from 0.1 micrometer to 10 micrometers, or even from 0.5micrometer to one micrometers; and/or have a width in a range of from0.001 micrometer to 26 micrometers, from 0.1 micrometer to 10micrometers, or even from 0.5 micrometer to 5 micrometers; and/or have athickness in a range of from 0.005 micrometers to 10 micrometers, orfrom 0.2 micrometers to 1.2 micrometers. In some embodiments, theceramic shaped abrasive particles may have an aspect ratio (length tothickness) of at least 2, 3, 4, 5, 6, or more. As used herein, length isthe longest particle dimension, width is the maximum particle dimensionperpendicular to the length, and thickness is perpendicular to lengthand width.

In embodiments wherein multiple shapes of the shaped ceramic abrasiveparticles are produced simultaneously, sieving may be useful to separatethe various particle sizes and/or shapes.

Shaped ceramic abrasive particles are useful, for example, in theconstruction of abrasive articles, including for example, agglomerateabrasive grain, coated abrasive articles (for example, conventional makeand size coated abrasive articles, slurry coated abrasive articles, andstructured abrasive articles), abrasive brushes, nonwoven abrasivearticles, and bonded abrasive articles such as grinding wheels, honesand whetstones.

For example, FIG. 9 shows an exemplary embodiment of a Type 27depressed-center grinding wheel 900 (i.e., an embodiment of a bondedabrasive article) according to one embodiment of the present disclosure.Center hole 912 is used for attaching Type 27 depressed-center grindingwheel 900 to, for example, a power driven tool. Type 27 depressed-centergrinding wheel 900 comprises shaped ceramic abrasive particles 920according to the present disclosure retained in binder 925. Examples ofsuitable binders include: organic binders such as epoxy binders,phenolic binders, aminoplast binders, and acrylic binders; and inorganicbinders such as vitreous binders.

In one exemplary embodiment of a coated abrasive article, the abrasivecoat may comprise a make coat, a size coat, and abrasive particles.Referring to FIG. 10, exemplary coated abrasive article 1000 has backing1020 and abrasive layer 1030. Abrasive layer 1030, includes abrasiveparticles 1040 according to the present disclosure secured to backing1020 by make layer 1050 and size layer 1060, each comprising arespective binder (e.g., epoxy resin, urethane resin, phenolic resin,aminoplast resin, acrylic resin) that may be the same or different.

In another exemplary embodiment of a coated abrasive article, theabrasive coat may comprise a cured slurry of a curable binder precursorand abrasive particles according to the present disclosure. Referring toFIG. 11, exemplary coated abrasive article 1100 has backing 1120 andabrasive layer 1130. Abrasive layer 1130 includes abrasive particles1140 and a binder 1145 (e.g., epoxy resin, urethane resin, phenolicresin, aminoplast resin, acrylic resin).

Techniques and materials for incorporating shaped ceramic abrasiveparticles according to the present disclosure into coated abrasivearticles according to the above embodiments will be apparent to those ofskill in the abrasive arts, and can be found in, for example, U.S. Pat.No. 4,314,827 (Leitheiser et al.); U.S. Pat. No. 4,652,275 (Bloecher etal.); U.S. Pat. No. 4,734,104 (Broberg); U.S. Pat. No. 4,751,137 (Tumeyet al.); U.S. Pat. No. 5,137,542 (Buchanan et al.); U.S. Pat. No.5,152,917 (Pieper et al.); U.S. Pat. No. 5,417,726 (Stout et al.); U.S.Pat. No. 5,573,619 (Benedict et al.); U.S. Pat. No. 5,942,015 (Culler etal.); and U.S. Pat. No. 6,261,682 (Law).

Nonwoven abrasive articles typically include a porous (e.g., a loftyopen porous) polymer filament structure having abrasive particles bondedthereto by a binder. An exemplary embodiment of a nonwoven abrasivearticle according to the present invention is shown in FIGS. 12A and12B, wherein lofty open low-density fibrous web 1200 is formed ofentangled filaments 1210 impregnated with binder 1220 (e.g., epoxyresin, urethane resin, phenolic resin, aminoplast resin, acrylic resin).Abrasive particles 1240 according to the present disclosure aredispersed throughout fibrous web 1200 on exposed surfaces of filaments1210. Binder 1220 coats portions of filaments 1210 and forms globules1250, which may encircle individual filaments or bundles of filaments,that adhere to the surface of the filament and/or collect at theintersection of contacting filaments, providing abrasive sitesthroughout the nonwoven abrasive article.

Techniques and materials for incorporating shaped ceramic abrasiveparticles according to the present disclosure into nonwoven abrasivearticles according to the above embodiments will be apparent to those ofskill in the abrasive arts, and can be found in, for example, U.S. Pat.No. 2,958,593 (Hoover et al.); U.S. Pat. No. 4,018,575 (Davis et al.);U.S. Pat. No. 4,227,350 (Fitzer); U.S. Pat. No. 4,331,453 (Dau et al.);U.S. Pat. No. 4,609,380 (Barnett et al.); U.S. Pat. No. 4,991,362 (Heyeret al.); U.S. Pat. No. 5,554,068 (Carr et al.); U.S. Pat. No. 5,712,210(Windisch et al.); U.S. Pat. No. 5,591,239 (Edblom et al.); U.S. Pat.No. 5,681,361 (Sanders); U.S. Pat. No. 5,858,140 (Berger et al.); U.S.Pat. No. 5,928,070 (Lux); U.S. Pat. No. 6,017,831 (Beardsley et al.);U.S. Pat. No. 6,207,246 (Moren et al.); and U.S. Pat. No. 6,302,930(Lux).

Techniques and materials for incorporating shaped ceramic abrasiveparticles according to the present disclosure into bonded abrasivearticles according to the above embodiments will be apparent to those ofskill in the abrasive arts, and can be found in, for example, U.S. Pat.No. 4,800,685 (Haynes et al.); U.S. Pat. No. 4,898,597 (Hay et al.);U.S. Pat. No. 4,933,373 (Moren); and U.S. Pat. No. 5,282,875 (Wood etal.).

Abrasive articles according to the present disclosure are useful forabrading a workpiece. Methods of abrading range from snagging (i.e.,high pressure high stock removal) to polishing (e.g., polishing medicalimplants with coated abrasive belts), wherein the latter is typicallydone with finer grades of abrasive particles. One such method includesthe step of frictionally contacting an abrasive article (e.g., a coatedabrasive article, a nonwoven abrasive article, or a bonded abrasivearticle) with a surface of the workpiece, and moving at least one of theabrasive article or the workpiece relative to the other to abrade atleast a portion of the surface.

Examples of workpiece materials include metal, metal alloys, exoticmetal alloys, ceramics, glass, wood, wood-like materials, composites,painted surfaces, plastics, reinforced plastics, stone, and/orcombinations thereof. The workpiece may be flat or have a shape orcontour associated with it. Exemplary workpieces include metalcomponents, plastic components, particleboard, camshafts, crankshafts,furniture, and turbine blades. The applied force during abradingtypically ranges from about 1 kilogram to about 100 kilograms.

Abrasive articles according to the present disclosure may be used byhand and/or used in combination with a machine. At least one of theabrasive article and the workpiece is moved relative to the other whenabrading. Abrading may be conducted under wet or dry conditions.Exemplary liquids for wet abrading include water, water containingconventional rust inhibiting compounds, lubricant, oil, soap, andcutting fluid. The liquid may also contain defoamers, degreasers, and/orthe like.

Examples of suitable binders include: organic binders such as epoxybinders, phenolic binders, aminoplast binders, and acrylic binders; andinorganic binders such as vitreous binders.

Select Embodiments of the Disclosure

In a first embodiment, the present disclosure provides a methodcomprising:

providing a layer of ceramic precursor material supported on a carrier,wherein the layer of ceramic precursor material comprises a ceramicprecursor and free water; and

cutting through the layer of ceramic precursor material using a laserbeam to provide shaped ceramic precursor particles.

In a second embodiment, the present disclosure provides a methodaccording to the first embodiment, wherein the method further comprises:

drying the shaped ceramic precursor particles to provide dried shapedceramic precursor particles;

calcining the dried shaped ceramic precursor particles to providecalcined shaped ceramic precursor particles; and

sintering the calcined shaped ceramic precursor particles to provideshaped ceramic abrasive particles.

In a third embodiment, the present disclosure provides a methodaccording to the second embodiment, wherein the shaped ceramic abrasiveparticles comprise alpha-alumina-based shaped ceramic abrasiveparticles.

In a fourth embodiment, the present disclosure provides a methodaccording to any one of the first to third embodiments, wherein thelayer of ceramic precursor material is provided by partially drying asol-gel layer.

In a fifth embodiment, the present disclosure provides a methodaccording to any one of the first to fourth embodiments, wherein thelayer of ceramic precursor material is substantially nonflowable due togravity.

In a sixth embodiment, the present disclosure provides a methodaccording to any one of the first to fifth embodiments, wherein thelayer of ceramic precursor material has a solids content in a range offrom 60 to 70 percent by weight.

In a seventh embodiment, the present disclosure provides a methodaccording to the first embodiment, further comprising:

drying the shaped ceramic precursor particles to provide dried shapedceramic precursor particles;

calcining the dried shaped ceramic precursor particles to providecalcined shaped ceramic precursor particles;

impregnating the calcined shaped ceramic precursor particles with animpregnating composition comprising a mixture comprising a second liquidmedium and at least one of a metal oxide or precursor thereof to provideimpregnated calcined shaped ceramic precursor particles, wherein theimpregnating composition impregnates the calcined shaped ceramicprecursor particles to a lesser degree on surfaces formed by the cuttingof the laser beam than other surfaces of the calcined shaped ceramicprecursor particles

In an eighth embodiment, the present disclosure provides a methodaccording to the seventh embodiment, further comprising:

sintering the impregnated calcined shaped ceramic precursor particles toprovide shaped ceramic abrasive particles.

In a ninth embodiment, the present disclosure provides a methodcomprising:

providing a layer of ceramic precursor material supported on a carrier,wherein the layer of ceramic precursor material comprises a ceramicprecursor and free water; and

scoring the layer of ceramic precursor material using a laser beam toprovide a scored layer of ceramic precursor material.

In a tenth embodiment, the present disclosure provides a methodaccording to ninth embodiment, further comprising:

breaking the scored layer of ceramic precursor material along scorelines to provide shaped ceramic precursor particles;

optionally calcining the shaped ceramic precursor particles to providecalcined shaped ceramic precursor particles; and

sintering the calcined shaped ceramic precursor particles or the shapedceramic precursor particles to provide shaped ceramic abrasiveparticles.

In an eleventh embodiment, the present disclosure provides a methodaccording to the tenth embodiment, wherein the scored layer of ceramicprecursor material is scored such that it forms a close-packed array oflatent abrasive precursor particles joined to one another along scorelines in the layer of ceramic precursor material.

In a twelfth embodiment, the present disclosure provides a methodaccording to the eleventh embodiment, further comprising:

forming boundary lines in the close-packed array of latent abrasiveprecursor particles by cutting through the layer of ceramic precursormaterial using the laser beam, wherein the boundary lines separateportions of the close-packed array of latent ceramic precursorparticles.

In a thirteenth embodiment, the present disclosure provides a methodaccording to the twelfth embodiment, further comprising:

deforming the carrier such that the portions of the close-packed arrayof latent abrasive precursor particles break along at least some of thescore lines to form the shaped ceramic precursor particles.

In a fourteenth embodiment, the present disclosure provides a methodaccording to the ninth embodiment, further comprising:

drying the scored layer of ceramic precursor material to provide a driedscored layer of ceramic precursor material;

breaking the dried scored layer of ceramic precursor material alongscore lines to provide dried shaped ceramic precursor particles;

optionally calcining the dried shaped ceramic precursor particles toprovide calcined shaped ceramic precursor particles; and

sintering the calcined shaped ceramic precursor particles or the driedshaped ceramic precursor particles to provide shaped ceramic abrasiveparticles.

In a fifteenth embodiment, the present disclosure provides a methodaccording to the fourteenth embodiment, wherein the layer of ceramicprecursor material is scored such that it forms a close-packed array oflatent dried ceramic precursor particles joined to one another alongscore lines in the layer of ceramic precursor material.

In a sixteenth embodiment, the present disclosure provides a methodaccording to the fifteenth embodiment, further comprising:

forming boundary lines in the close-packed array of latent dried ceramicprecursor particles by cutting through the layer of ceramic precursormaterial using the laser beam, wherein the boundary lines separateportions of the close-packed array of latent dried ceramic precursorparticles.

In a seventeenth embodiment, the present disclosure provides a methodaccording to the sixteenth embodiment, wherein said breaking the scoredlayer of ceramic precursor material along score lines is caused at leastin part by deforming the carrier such that the portions of theclose-packed array of latent ceramic precursor particles break along atleast some of the score lines to form the dried shaped ceramic precursorparticles.

In an eighteenth embodiment, the present disclosure provides a methodaccording to any one of the tenth to seventeenth embodiments, whereinthe shaped ceramic abrasive particles comprise alpha-alumina-basedshaped ceramic abrasive particles.

In a nineteenth embodiment, the present disclosure provides a methodaccording to any one of the ninth to eighteenth embodiments, wherein thelayer of ceramic precursor material is provided by partially drying asol-gel layer.

In a twentieth embodiment, the present disclosure provides a methodaccording to any one of the ninth to nineteenth embodiments, wherein thelayer of ceramic precursor material is substantially nonflowable due togravity.

In a twenty-first embodiment, the present disclosure provides a methodaccording to any one of the ninth to twentieth embodiments, wherein thelayer of ceramic precursor material has a solids content in a range offrom 60 to 70 percent by weight.

In a twenty-second embodiment, the present disclosure provides a methodaccording to any one of the ninth to twenty-first embodiments, whereinthe laser beam is generated by an infrared fiber laser.

In a twenty-third embodiment, the present disclosure provides a methodaccording to any one of the ninth to twenty-second embodiments, whereinthe ceramic precursor material further comprises an absorber thatabsorbs incident electromagnetic radiation of the laser beam andconverts it into heat.

In a twenty-fourth embodiment, the present disclosure provides a methodaccording to the twenty-third embodiment, wherein the absorber has amolar extinction coefficient at of least 10,000 M-1 cm⁻¹ at primarywavelengths of the laser beam.

In a twenty-fifth embodiment, the present disclosure provides a methodaccording to the twenty-third or twenty fourth embodiment, wherein theabsorber is present in sufficient amount to absorb at least 30 percentof the incident electromagnetic radiation of the laser beam.

In a twenty-sixth embodiment, the present disclosure provides shapedceramic abrasive particles prepared according to the method of any oneof the first to twenty-fifth embodiments.

In a twenty-seventh embodiment, the present disclosure provides shapedceramic abrasive particles, wherein each of the shaped ceramic abrasiveparticles independently comprises a body member and at least threerod-shaped members extending from the body member.

In a twenty-eighth embodiment, the present disclosure provides shapedceramic abrasive particles according to the twenty-seventh embodiment,wherein each one of the at least three rod-shaped members has across-sectional profile independently selected from a circle, anellipse, a square, a rectangle, or a triangle.

In a twenty-ninth embodiment, the present disclosure provides shapedceramic abrasive particles according to the twenty-seventh ortwenty-eighth embodiment, wherein the at least three rod-shaped membersare out of plane with the body member, and wherein the at least threerod-shaped members extend from the same side of the body member.

In a thirtieth embodiment, the present disclosure provides shapedceramic abrasive particles according to any one of the twenty-seventh totwenty-ninth embodiments, wherein the shaped ceramic abrasive particlescomprise alpha-alumina.

In a thirty-first embodiment, the present disclosure provides shapedceramic abrasive particles according to any one of the twenty-seventh tothirtieth embodiments, wherein the body member has an opening therein.

In a thirty-second embodiment, the present disclosure provides shapedceramic abrasive particles according to any one of the twenty-seventh tothirty-first embodiments, wherein said at least three rod-shaped memberscomprises first, second, third, fourth, fifth, six, seventh, and eighthrod-shaped members.

In a thirty-third embodiment, the present disclosure provides shapedceramic abrasive particles according to any one of the twenty-seventh tothirty-second embodiments, wherein the shaped ceramic abrasive particlescomprise alpha-alumina.

In a thirty-fourth embodiment, the present disclosure provides shapedceramic abrasive particles according to any one of the twenty-seventh tothirty-third embodiments, wherein the shaped ceramic abrasive particleshave a size distribution corresponding to an abrasives industryrecognized nominal grade.

In a thirty-fifth embodiment, the present disclosure provides shapedceramic abrasive particles, wherein each of the shaped ceramic abrasiveparticles has a body portion bounded by a peripheral loop portion havinga roughened surface texture as compared to the body portion.

In a thirty-sixth embodiment, the present disclosure provides shapedceramic abrasive particles according to the thirty-fifth embodiment,wherein the shaped ceramic abrasive particles have a size distributioncorresponding to an abrasives industry recognized nominal grade.

In a thirty-seventh embodiment, the present disclosure provides shapedceramic abrasive particles according to the thirty-fifth or thirty-sixthembodiment, wherein the shaped ceramic abrasive particles comprisealpha-alumina.

In a thirty-eighth embodiment, the present disclosure provides shapedceramic precursor particles, wherein the shaped ceramic precursorparticles have a peripheral loop portion encircling and abutting aninterior portion, and wherein the peripheral loop portion comprisesalpha alumina, and the interior portion comprises an alpha aluminaprecursor and is free of alpha alumina.

In a thirty-ninth embodiment, the present disclosure provides shapedceramic precursor particles according to the thirty-eighth embodiment,wherein the alpha alumina precursor comprises a boehmite gel.

In a fortieth embodiment, the present disclosure provides shaped ceramicabrasive particles, wherein the shaped ceramic abrasive particles have aperipheral loop portion encircling and abutting, but not fullyenclosing, an interior portion, and wherein the peripheral loop portionhas a different microcrystalline structure than the interior portion.

In a forty-first embodiment, the present disclosure provides shapedceramic abrasive particles according to the fortieth embodiment, whereinthe shaped ceramic abrasive particles have a size distributioncorresponding to an abrasives industry recognized nominal grade.

In a forty-second embodiment, the present disclosure provides a bondedabrasive article comprising the shaped ceramic abrasive particlesaccording to the fortieth or forty-first embodiment retained in abinder.

In a forty-third embodiment, the present disclosure provides shapedceramic precursor particles, wherein each of the shaped ceramicprecursor particles has first and second opposed nonadjacent majorsurfaces, a peripheral surface extending between the first and secondmajor surfaces, wherein the peripheral surface comprises an ablatedregion extending along the peripheral surface adjacent to the firstmajor surface but not contacting the second major surface, and afractured region extending along the peripheral surface adjacent thesecond major surface but not contacting the first major surface.

In a forty-fourth embodiment, the present disclosure provides shapedceramic precursor particles according to the forty-third embodiment,wherein the fractured region has an area greater than that of theablated region.

In a forty-fifth embodiment, the present disclosure provides shapedceramic precursor particles according to the forty-third or forty-fourthembodiment, wherein the shaped ceramic precursor particles comprise analpha alumina precursor.

In a forty-sixth embodiment, the present disclosure provides shapedceramic abrasive particles, wherein each of the shaped ceramic abrasiveparticles has first and second opposed nonadjacent major surfaces, aperipheral surface extending between the first and second majorsurfaces, wherein the peripheral surface comprises an ablated regionextending along the peripheral surface adjacent to the first majorsurface but not contacting the second major surface, and a fracturedregion extending along the peripheral surface adjacent the second majorsurface but not contacting the first major surface.

In a forty-seventh embodiment, the present disclosure provides shapedceramic abrasive particles according to the forty-sixth embodiment,wherein the fractured region has an area greater than that of theablated region.

In a forty-eighth embodiment, the present disclosure provides shapedceramic abrasive particles according to the forty-sixth or forty-seventhembodiment, wherein the shaped ceramic abrasive particles comprise alphaalumina.

In a forty-ninth embodiment, the present disclosure provides shapedceramic abrasive particles according to any one of the forty-sixth toforty-eighth embodiments, wherein the shaped ceramic abrasive particleshave a size distribution corresponding to an abrasives industryrecognized nominal grade.

In a fiftieth embodiment, the present disclosure provides a bondedabrasive article comprising the shaped ceramic abrasive particles of anyone of the forty-ninth to fifty-second embodiments retained in a binder.

In a fifty-first embodiment, the present disclosure provides shapedceramic abrasive particles, wherein each of the shaped ceramic abrasiveparticles comprises first and second opposed major surfaces that areconnected by first and second opposed sides and first and second opposedends, wherein the first and second opposed major surfaces aresubstantially smooth, wherein the first and second opposed sides and thefirst and second opposed ends have a surface topography comprisingtortuous rounded micrometer-scale projections and depressions, whereinthe first side abuts the first major surface forming an acute dihedralangle, and wherein the second side abuts the first major surface formingobtuse dihedral angle.

Objects and advantages of this disclosure are further illustrated by thefollowing non-limiting examples, but the particular materials andamounts thereof recited in these examples, as well as other conditionsand details, should not be construed to unduly limit this disclosure.

EXAMPLES

Unless otherwise noted or inappropriate, all parts, percentages, ratios,etc. in the Examples and the rest of the specification are by weight.

Comparative Example A

A boehmite gel was made by dispersing aluminum oxide monohydrate powderhaving the trade designation “DISPERAL” (Sasol North America of Houston,Tex.) by continuous mixing in a solution containing water and 1.86percent nitric acid at 125° F. (52° C.). The resulting sol-gel was 40percent by weight solids.

The resulting sol-gel was coated onto either release paper, polyesterfilm or stainless steel substrates to form a layer of ceramic precursormaterial using a 6 in×6 in opening×0.030 in thick (15.24 cm×15.24cm×0.762 mm thick) polycarbonate template and an 8-inch drywall jointknife to form a gel sheet for converting.

A pulsed CO₂ laser (Coherent Diamond 84 Series industrial CO₂ laser,Coherent Inc., Santa Clara, Calif.) was used to cut the gel sheet intoequilateral triangular shapes having 110 mil (2.8 mm) sides. The laserwas set to trace the triangular pattern twice at a scan speed of 1000mm/sec, a first-pass pulse duration of 30 microseconds, a pulsefrequency of 10 kHz, and a second-pass pulse duration of 20microseconds.

Attainment of precise shapes was not possible under these conditions.

Example 1

The procedure of Comparative Example A was repeated, except that theambient drying time of the gel sheet was increased to 30 minutes, and astainless steel substrate was used. FIG. 13 shows the gel sheetimmediately after laser cutting.

Example 2

The procedure of Comparative Example A was repeated, except that theambient drying time of the layer of ceramic precursor material wasincreased to 2 hours, and a polyester film substrate was used. FIG. 14shows the gel sheet immediately after laser cutting.

The particles were sintered (fired) at 1400° C. in a tube furnace. Theresulting sintered particles had a true density of 3.950 g/cm³ and wereabout 0.332 mm thick and had a side length of about 1.80 mm. FIG. 15 isan SEM photomicrograph of the sintered particles.

Example 3

Two 7-inch (18-cm) diameter×⅞-inch (2.2-cm) center hole abrasive discsincluding the sintered abrasive particles of Example 2 were prepared.The discs were prepared on vulcanized fiber backings using a phenolicmake coating consisting of 49 parts of a 75 percent solids aqueoussolution of phenol-formaldehyde resin (having a phenol:formaldehyderatio of 1.5 to 2.1:1 catalyzed with 2.5 percent potassium hydroxide),41 parts calcium carbonate (“HUBERCARB Q325” from J.M. HuberCorporation, Edison, N.J.), and 10 parts water. The abrasive particlesof Example 2 were electrostatically coated onto the make coating and asize coating [consisting of 29 parts of a 75 percent solids aqueoussolution of phenol-formaldehyde resin (having a phenol:formaldehyderatio of 1.5 to 2.1:1 catalyzed with 2.5 percent potassium hydroxide),51 parts filler (“CRYOLITE TYPE RTN-C” from Koppers Trading ofPittsburgh, Pa.), 2 parts iron oxide pigment, and 18 parts water] wasapplied. All coating weights are shown in Table 1 (below). Followingcuring, the discs were evaluated for abrasive performance.

TABLE 1 PHENOLIC SIZE MAKE COAT MINERAL WEIGHT DISC TEST DISC WT (WET)WEIGHT (WET) WEIGHT METHOD 1 3.9 g 17.2 g 15.3 g 58.6 g 1 2 4.5 g 17.215.5 g 59.1 g 2

Each disc was tested according to the method indicated in Table 1.Comparative Disc A was a commercially-available grade 36 fiber disc(“988C grade 36” from 3M Company of St. Paul, Minn.). A new ComparativeDisc A was used for each test.

Abrasion Testing Test Method 1—Swing Arm Test

The abrasive disc to be evaluated was attached to a 20.3 cm circularbackup plate, commercially available as Part No. 05114145192 from 3MCompany. The backup plate was then secured to a testing device obtainedunder the trade designation “SWING ARM TESTER” from Reel Manufacturing,Centerville, Minn., using a metal screw fastener. A 14-gauge (1.9 mm)1010 steel disc-shaped work piece with a 30.5 cm diameter and 1.897 mmthickness was weighed and secured to the testing device with a metalfastener. During each test, the steel workpiece was applied to theabrasive article disc with a load of 2910 grams. The abrasive articledisc was rotated at 3500 revolutions per minute (rpm), and the workpiecewas placed against the disc at an angle of 18.5 degrees for up to 8one-minute intervals, while the workpiece was rotated at 2 rpm. The testendpoint was determined when the incremental cut fell below 40 percentof the initial cut. The amount of steel removed (total swing-arm cut)was recorded.

Test Method 2—Slide Action Test

The abrasive disc to be evaluated was used to grind the face of a 1.25cm by 18 cm 1018 mild steel workpiece. The grinder used was a constantload hydraulic disc grinder. A constant load between each workpiece andabrasive disc was maintained at 7.26 kg (16 pounds) force. The back-uppad for the grinder was an aluminum back-up pad. The disc was secured tothe aluminum pad by a retaining nut and was driven at 5000 rpm. Duringoperation, the test disc was tilted (“heeled”) at approximately 7degrees to present an abrasive band extending from the edge and in 3.5cm towards the center to the workpiece. During testing, the workpiecewas traversed along its length at a rate of about 8.4 cm per second.Each disc was used to grind a separate workpiece for successive60-second intervals. Cut was determined for additional 60-secondgrinding intervals until an endpoint was reached. The endpoint wasdetermined when cut during a one-minute test interval fell below 70percent of the cut of the initial test interval or when the discintegrity was compromised. The test results are reported in Table 2(below).

TABLE 2 TIME TO TEST CUT, END-OF-TEST, SPECIMEN METHOD grams minutesDisc 1 1 382.5 5 Comp. Disc A 1 155.3 3 Disc 2 2 3387.5 30 Comp. Disc A2 959.5 10

Example 4

A boehmite gel was made by dispersing aluminum oxide monohydrate powderhaving the trade designation “DISPERAL” (Sasol North America, Houston,Tex.) by continuous mixing in a solution containing water and 1.86percent nitric acid at 125° F. (52° C.). The resulting sol-gel was 40percent by weight solids.

Sheets (100 mm×150 mm×1.5 mm thick) of the resulting sol-gel were castonto sheet metal that was covered with Cut-Right wax paper from ReynoldsKitchens of Richmond, Va. using an acrylic knife (3.09 mmthickness×44.57 mm width×300 mm length) into a polycarbonate templatethat was 1.5 mm thick with a 100 mm wide×150 mm long.

Within 5 minutes of casting, the sheets were covered with a piece of20-lb (9.1-kg) copy paper. The assembly was then allowed to dry atambient conditions for 1-2 hours, allowing the gel to dry until it had asolids content of about 70 percent by weight. The gel sheet was cutusing a Coherent DIAMOND E-SERIES 400 pulsed CO₂ laser from Coherent,Inc. of Santa Clara, Calif., using Nutfield WAVERUNNER software andPIPELINE controller (from Nutfield Technology of Hudson, N.H.), set to50 kHz, 10 percent duty cycle (2 μS), to give 48.8 watts of power and ascan rate of 1 m/s with delays set at 4 ms Jump, 1 ms mark, 0.4 ms ply,1.2 ms laser on, 1.5 ms laser off with a jump rate of 7 m/s using anested “tic-tac-toe” pattern (shown as pattern 1600 in FIG. 16, whereinthe maximum dimension was 6.67 mm) using a power of 48.8 watts and ascan rate of one meter per second (1 m/s). The cut sheets were dried at69° F. (21° C.) for 3 days.

The cut shapes were then liberated from the sheet, and the resultingseparated dried shaped ceramic precursor particles were then calcined atapproximately 650° C., and then saturated with a mixed nitrate solutioncontaining 1.4 percent as MgO, 1.7 percent as Y₂O₃, 5.7 percent asLa₂O₃, and 0.07 percent as CoO impregnated at a level 70 percent byweight based on the weight of calcined gel. Once the calcined shapedceramic precursor particles were impregnated, the particles were allowedto dry after which the particles were again calcined at 650 degreesCelsius and sintered at approximately 1400° C. Both the calcining andsintering were performed using box furnaces. A representative resultingshaped ceramic abrasive particle is shown at two magnifications in FIGS.7A and 7B.

Example 5

TETRAARYLDIAMINE (IR dye, product code FHI 104422P, from Fabric ColorHolding Company, Paterson, N.J.) was mixed at 0.08 percent by weightwith boehmite sol gel prepared as in Comparative Example A. Theresultant modified sol gel was coated on a flat polyethyleneterephthalate polyester film with thickness 50 mil (1.27 mm). Theresultant layer was cut using an 20-watt pulsed fiber laser from SPILasers, Southampton, United Kingdom. The laser wavelength was 1.06micrometers. Waveform #1 was used. The laser pulse repetition rateselected was 65 kHz. At full power (100 percent), the laser output(average power) was measured 12.8 watts. The laser was directed using aHURRYSCAN 14 laser scanner from Scanlab AG, Munich, Germany, equippedwith a telecentric lens having a focal length of 163 mm. The focusedspot size on the layer of sol gel was estimated to be about 10micrometers. The laser was vertically incident to the sol gel sheetsurface. Parallel lines were cut in three directions with 60 degree withrespect to each other, resulting in an array of close packed triangularshaped ceramic precursor particles. The laser power was set at 95percent (12.1 W power). The line spacing was 259 micrometers, and thelaser traverse speed was 300 mm/sec. A representative particle (shown inFIG. 4) was removed from the cut sol gel sheet and examined via SEM. Thetop edge (facing the laser) showed artifacts of ablation, and the bottomportion of particle edge was fractured.

Example 6

TETRAARYLDIAMINE (IR dye, product code FHI 104422P, from Fabric ColorHolding Company, Paterson, N.J.) was mixed at 0.13 percent by weightwith boehmite sol gel prepared as in Comparative Example A, and a highspeed mixer was used to stir the solution for 10 minutes. The resulting0.25 percent by weight dye-doped solution was green in color. The dopedsol gel was aged in a plastic bottle for one hour before coating. Athree-inch (8-cm) wide square applicator with 50 mils (1.27 mm) coatingslot was placed on a 5 in×10 in×5 mil (12.7 cm×25.4×127 micrometer)sheet of polyethylene terephthalate (PET) film. Thirty (30) grams of thedoped solution was placed into the middle of the applicator and appliedto the sheet of PET film resulting in a 50 mil (1.27 mm) layer of solgel coating on the surface of the PET sheet. The sol gel coating wasleft to dry at room conditions for 15 minutes. The resultant layer wascut using an 20-watt pulsed fiber laser from SPI Lasers. The laserwavelength was 1.07+/−0.01 micrometers. Waveform #0 was used. The laserpulse repetition rate selected was 30 kHz. At 90 percent power, thelaser output (average power) was measured 12.8 watts. The laser pulsewidth was measured around 200 nanoseconds (nsec). The laser was directedusing a HURRYSCAN 14 laser scanner from Scanlab AG, Munich, Germany,equipped with a telecentric lens having a focal length of 163 mm. Thefocused spot size on the layer of sol gel was estimated to be about 10micrometers. The laser was vertically incident to the sol gel sheetsurface. Parallel lines were cut in three directions with 60 degree withrespect to each other, resulting in an array of close packed triangularshaped ceramic precursor particles. The line spacing was 93.5 mil (2.37mm). The laser traverse speed was 1000 mm/sec. FIG. 17A shows anexemplary resulting shaped ceramic precursor particle from the aboveprocedure. FIG. 17B shows an exemplary resulting shaped ceramicprecursor particle from the above procedure after subsequent sintering.FIG. 17C shows an exemplary resulting shaped ceramic precursor particlefrom the above procedure after subsequent calcining and sintering.

Example 7

TETRAARYLDIAMINE (IR dye, product code FHI 104422P, from Fabric ColorHolding Company, Paterson, N.J.) was mixed at 0.24 percent by weightwith boehmite sol gel prepared as in Comparative Example A, and a highspeed mixer is used to stir the solution for 10 minutes. A three-inch(8-cm) width of square applicator with 50 mils coating slot was placedon a 5 in×10 in×5 mil (12.7 cm×25.4×127 micrometer) sheet ofpolyethylene terephthalate (PET) film. Dye-doped solution was placedinto the middle of the applicator and applied to the sheet of PET filmresulting in a 50 mil (1.27 mm) layer of sol gel coating on the surfaceof the PET sheet. Sol-gel coating will be left to dry for 3 hours (from10:19 am to 1:19 pm) under normal room condition before laser cuttingexperiment. The resultant layer was cut using an 40-watt pulsed fiberlaser from SPI Lasers. The laser wavelength was 1.07+/−0.01 micrometers.Waveform #2 was used. The laser pulse repetition rate selected was 76kHz. At 100 percent power, the laser output (average power) was measured40.3 watts. The laser pulse width was measured around 60 nsec. The laserwas directed using a HURRYSCAN 25 laser scanner from Scanlab AG, Munich,Germany. The focused spot size on the layer of sol gel was estimated tobe about 10 micrometers.

In order to achieve angle cut, the PET film was tilted at an angle of 45degrees relative to the laser beam. The line spacing was 1 mm in the ydirection and 10 mm in the x direction. Since the stage was tilted at 45degrees, only portion of lines along the y direction was in focus. Tocut the sol-gel layer, about 50 percent of the laser power (i.e., around20 W average power at 76 kHz) and the laser line scan speed of 75 mm/secwas used. After laser cutting, the sample was left to dry 1 day, thegrains were separated the resultant shaped ceramic precursor particlewas viewed by scanning electron microscopy (SEM) and is shown in FIG.8B.

Example 8

TETRAARYLDIAMINE (IR dye, product code FHI 104422P, from Fabric ColorHolding Company, Paterson, N.J.) was mixed at 0.08 percent by weightwith boehmite sol gel prepared as in Comparative Example A. Theresultant modified sol gel was coated on a flat polyethyleneterephthalate polyester film with thickness 10 mils. The resultant layerwas cut using an 20-watt pulsed fiber laser from SPI Lasers. The laserwavelength was 1.06 micrometers. Waveform #1 was used. The laser pulserepetition rate selected was 65 kHz. At full power (100 percent), thelaser output (average power) was measured 12.8 watts. The laser wasdirected using a HURRYSCAN 14 laser scanner from Scanlab AG equippedwith a telecentric lens having a focal length of 163 mm. The focusedspot size on the layer of sol gel was estimated to be about 10micrometers. The laser was vertically incident to the sol gel sheetsurface. Parallel lines were cut in three directions with 60 degree withrespect to each other, resulting in an array of close packed triangularshaped ceramic precursor particles. The line spacing was 93.5 mil (2.37mm). The laser traverse speed was 200 mm/sec.

The resultant laser-cut shaped ceramic precursor particles werecollected, calcined at approximately 650 degrees Celsius and thensaturated with a mixed nitrate solution of the following concentration(reported as oxides): 1.8 percent each of MgO, Y₂O₃, Nd₂O₃ and La₂O₃.The excess nitrate solution was removed and the saturated precursorlaser cut shaped abrasive particles were allowed to dry after which theparticles were again calcined at 650 degrees Celsius and sintered atapproximately 1400 degrees Celsius. Both the calcining and sintering wasperformed using a RAPID TEMP FURNACE box kiln (CM Inc., Bloomfield,N.J.). The resulting microstructure from a representative resultantshaped ceramic abrasive particle is shown in FIGS. 18A and 18B. Theunique and unexpected microstructure along the laser cut edges showed noapparent evidence of the MgO, Y₂O₃, Nd₂O₃ and La₂O₃ dopants indicatingthat the laser-cut edge was converted to alpha-alumina as a result ofthe heat generated by laser cutting. Once fired to a dense and virtuallynon-porous alpha-alumina, the laser cut edges were unable to absorb thedopants. The microstructure of the laser-cut edges (e.g., see FIG. 18B)showed approximately 8- to 15-micrometer densified alpha-alumina cellsbelieved to be produced by the extremely rapid heating of the laser cutedges. Conversely, the interior of the particle (shown in FIG. 18A)exhibit the expected microstructure resulting from absorption of theMgO, Y₂O₃, Nd₂O₃ and La₂O₃ dopants into the porous alpha-aluminaprecursor and when sintered produced the platelet structures formedwithin the surrounding alpha-alumina matrix.

Example 9 and Comparative Examples B-C

Example 9 and Comparative Examples B-C demonstrate the relative abradingeffectiveness over time for the inventive abrasive particles compared tothose of precision-molded abrasive particles and prior art abrasiveparticles.

Example 9 Preparation of Abrasive Particles

A boehmite gel was made by dispersing aluminum oxide monohydrate powderhaving the trade designation “DISPERAL” (from Sasol North America) bycontinuous mixing in a solution containing water and 1.86 percent nitricacid at 125° F. (52° C.). The resulting sol-gel was 40 percent by weightsolids.

Sheets (100 mm×150 mm×1.5 mm thick) of the resulting sol-gel were castonto sheet metal that was covered with CUT-RIGHT wax paper from ReynoldsKitchens, Richmond, Va. using an acrylic knife (3.09 mm thickness×44.57mm width×300 mm length) into a polycarbonate template that was 1.5 mmthick with a 100 mm wide×150 mm long. The cast sheets were allowed todry at ambient conditions for 30 minutes.

The resultant gel sheets were cut using a Coherent DIAMOND E-SERIES 400pulsed CO₂ laser from Coherent, Inc., Santa Clara, Calif., usingNutfield WAVERUNNER software and PIPELINE controller (from NutfieldTechnology), set to 50 kHz, 8 percent duty cycle (1.5 μs), to give 25watts of power and a scan rate of 500 mm/s with a spot size of 220 μm.The scan grid was 1000 mm×1000 mm and the scanned pattern was trianglesof dimensions 2.77 mm×2.77 mm×2.77 mm×0.77 mm thick. The cut sheets wereair dried at ambient conditions. The cut shapes were then liberated fromthe sheet, and the resulting separated dried shaped ceramic precursorparticles were then calcined at approximately 650° C., and thensaturated with a mixed nitrate solution containing 1.4 percent as MgO,1.7 percent as Y₂O₃, 5.7 percent as La₂O₃ and 0.07 percent as CoOimpregnated at a level 70 percent by weight based on the weight ofcalcined gel. Once the calcined shaped ceramic precursor particles wereimpregnated, the particles were allowed to dry after which the particleswere again calcined at 650 degrees Celsius and sintered at approximately1400° C. Both the calcining and sintering were performed using boxfurnaces. The resulting triangular-shaped particles were similar indimensions to the particles of Comparative Example B.

Preparation of Coated Abrasive Discs

A precut vulcanized fiber (obtained under the trade designation “DYNOSVULCANIZED FIBRE” from DYNOS GmbH, Troisdorf, Germany) disc blank with adiameter of 7 inches (17.8 cm), having a center hole of ⅞ inch (2.2 cm)diameter and a thickness of 0.83 mm (33 mils) was used as the abrasivesubstrate. The fiber disc was coated by brush with a phenolic make resin(which was prepared by mixing 49.2 parts by weight of a base-catalyzed(2.5 percent KOH) 1.5:1 to 2.1:1 phenol-formaldehyde condensate (75percent in water), 40.6 parts by weight of CACO, and 10.2 parts byweight deionized water) to a weight of 3.8+/−0.5 grams. 17.3 grams ofabrasive particles was applied using an electrostatic coater. The discwas heated at 90° C. for 1 hour followed by 103° C. for 3 hours. Thediscs were then coated by brush with a size resin prepared by mixing40.6 parts by weight of a base-catalyzed (2.5 percent KOH) 1.5:1 to2.1:1 phenol-formaldehyde condensate (75 percent in water); 69.9 partsby weight of cryolite (obtained as “CRYOLITE TYPE RTN-C” from KoppersTrading, Pittsburgh, Pa.); 2.5 parts by weight of red iron oxidepigment; and 25 parts by weight deionized water. Excess size resin wasremoved with a dry brush until the flooded glossy appearance was reducedto a matte appearance. The size coating weight was 17.1 grams. The discwas heated for 90 minutes at 90° C., followed by 16 hours at 103° C. Thecured disc was orthogonally flexed over a 1.5 inch (3.8 cm) diameterroller and allowed to equilibrate with ambient humidity for 1 weekbefore testing. the resulting disc is Example 8.

Comparative Example B

Comparative Example B was prepared identically to Example 8 with theexceptions that 1) the abrasive particles were shaped alpha aluminaabrasive particles produced from a mold having triangular shaped moldcavities of 28 mils depth (0.71 mm) and 110 mils (2.79 mm) on each side,producing triangular shaped abrasive particles approximately 1.5 mm longon each side of the larger triangular face, approximately 0.3 mm thick,having about a 98-degree included angle for the slope of the edges,approximately grade 36+, as disclosed in U.S. Pat. Appl. Publ. No.2010/0151196 A1 (Adefris et al.); 2) make coat weight was 3.2 grams; 3)the abrasive particle coat weight was 16.9 grams; and 4) the size coatweight was 13.9 grams.

Comparative Example C

Comparative Example C was a commercially available grinding disc,obtained as “NORTON SG BLAZE F980 FIBER DISC, 7 in×⅞ in, grade 36” fromSaint-Gobain Abrasives North America, Worcester, Mass.

Abrasion Testing Test Method 3

The abrasive discs were tested using the following procedure. 7-Inch(17.8 cm) diameter abrasive discs for evaluation were attached to arotary grinder fitted with a 7-inch (17.8 cm) ribbed disc pad face plate(“80514 EXTRA HARD RED” obtained from 3M Company). The grinder was thenactivated and urged against an end face of a 0.75×0.75 in (1.9×1.9 cm)pre-weighed 1045 steel bar under a load of 10 lb (4.5 kg). The resultingrotational speed of the grinder under this load and against thisworkpiece was 5000 rpm. The workpiece was abraded under these conditionsfor a total of one hundred (100) 20-second grinding intervals (cycles).Following each 20-second cycle, the workpiece was allowed to cool toroom temperature and weighed to determine the cut of the abrasiveoperation. Test results were reported as the incremental cut for eachinterval and the total cut removed as shown in Table 3. For ComparativeExample B and Comparative Example C, two discs were tested. The Example8 disc showed sustained cut that was superior to that of ComparativeExample C and initially achieved cut comparable to Comparative ExampleB.

TABLE 3 INCREMENTAL CUT, grams COM- COM- COM- COM- PAR- PAR- PAR- PAR-ATIVE ATIVE ATIVE ATIVE EXAM- EXAM- EXAM- EXAM- EXAM- CYCLES PLE 8 PLEB(1) PLE B(2) PLE C(1) PLE C(2)  1 21.42 21.01 20.87 16.45 15.46  221.68 22.83 22.31 14.82 14.03  3 20.69 23.54 23.63 14.45 13.81  4 19.9623.64 25.83 14.77 13.42  5 20.14 25.15 26.70 14.64 13.25  6 20.63 26.2826.78 14.58 12.92  7 20.37 26.89 26.91 13.99 12.59  8 19.27 27.89 26.8514.29 12.59  9 19.4 27.25 26.31 14.05 12.56 10 19.25 26.94 26.33 1412.76 11 20.01 26.46 26.04 13.88 12.76 12 19.66 27.37 25.57 14.28 12.5813 19.69 27.41 25.91 14.55 12.92 14 20.17 27.09 26.15 14.45 12.89 1519.65 26.5 26.31 14.36 13.19 16 19.21 27.02 25.34 13.94 13.34 17 19.1527.42 25.31 14.12 13.42 18 18.83 27.85 25.96 14.24 13.78 19 19.03 27.2425.97 14.11 14.05 20 19.81 27.09 25.7 14.23 14.28 21 20.45 27.38 25.1614.54 13.59 22 19.87 27.38 25.45 14.33 13.31 23 19.83 27.07 25.08 14.3913.52 24 19.49 26.85 25.12 14.01 13.55 25 19.44 27.15 25.03 13.87 13.4726 19.04 27.46 24.97 13.95 13.79 27 18.65 27.31 25.12 13.94 14.02 2818.45 26.83 24.85 13.9 13.99 29 18.35 26.78 25.11 14.08 13.85 30 18.3626.77 25.22 14.18 13.46 31 18.29 27.2 25.31 14.38 13.52 32 18.26 26.6325.48 13.69 13.37 33 17.36 26.73 24.6 13.92 13.22 34 17.39 26.55 24.6113.77 13.22 35 17.21 26.44 24.54 13.76 13.61 36 16.81 25.84 24.55 13.613.8 37 16.73 25.25 24.44 13.4 13.58 38 16.81 24.59 23.39 13.2 13.55 3916.94 24.79 23.94 13.06 13.44 40 16.74 25.23 23.46 12.91 13.06 41 17.2624.84 23.43 13.02 12.88 42 17.11 25.1 23.21 12.83 12.9 43 17.01 25.1223.01 12.73 12.94 44 16.88 24.43 23.15 12.45 12.66 45 16.73 24.56 23.3611.98 12.66 46 16.85 24.65 23.83 11.81 12.4 47 16.62 24.2 23.67 11.612.38 48 16.34 23.94 23.89 11.36 12.3 49 16.22 23.76 23.9 11.14 11.99 5016.13 23.63 23.95 10.83 11.68 51 16.14 23.45 23.7 10.72 11.63 52 15.9123.21 23.58 10.36 11.31 53 15.89 23.09 23.47 10.23 11.2 54 15.56 23.0723.59 9.97 11.02 55 15.54 23.15 23.61 9.68 10.68 56 15.39 23.15 23.29.29 10.58 57 15.06 22.54 23.44 8.79 10.37 58 14.86 22.79 23.15 8.2910.11 59 14.7 22.89 23.11 7.72 9.91 60 14.31 22.79 22.78 7.41 9.79 6113.74 22.16 22.48 7.25 9.34 62 13.53 22.24 22.24 7.13 8.82 63 13.4822.12 21.8 7.11 8.32 64 13.29 21.72 21.85 7.02 7.93 65 13.11 21.55 21.646.85 7.47 66 12.88 21.43 21.82 6.71 7.25 67 13 21.16 21.82 6.53 6.93 6812.71 20.76 21.77 6.4 6.8 69 12.55 20.41 21.57 6.3 6.69 70 12.28 20.3221.49 6.25 6.59 71 12.03 20.07 21.06 6.17 6.5 72 11.58 19.88 21.14 6.146.38 73 11.17 19.43 20.73 6.02 6.4 74 11.04 19.23 20.36 5.96 6.23 7510.72 18.92 20.62 5.87 6.23 76 10.42 18.62 20.7 5.87 6.18 77 9.89 18.1620.6 5.84 6.18 78 9.41 18.01 20 5.84 6.04 79 9.22 17.66 20 5.81 6.05 808.96 17.28 20.11 5.7 6.01 81 8.7 16.92 20.07 5.69 5.98 82 8.42 16.3219.82 5.68 5.97 83 8.26 15.83 19.34 5.66 5.85 84 8.06 15.83 19.04 5.665.87 85 7.79 15.67 19.51 5.62 5.78 86 7.61 15.29 19.46 5.58 5.73 87 7.4114.99 19.27 5.58 5.71 88 7.25 14.91 19.26 5.59 5.75 89 7.1 14.67 19.235.55 5.72 90 7.04 14.38 19.13 5.55 5.69 91 7.06 14.09 19.07 5.42 5.65 926.99 13.83 18.97 5.43 5.59 93 6.95 13.48 19 5.39 5.5 94 6.83 13.07 18.915.31 5.5 95 6.71 12.87 18.83 5.32 5.48 96 6.67 12.55 18.73 5.24 5.47 976.48 12.38 18.82 5.25 5.38 98 6.41 12.13 18.82 5.28 5.36 99 6.34 11.918.59 5.32 5.37 100  6.3 11.76 18.39 5.29 5.35 total cut 1054 2069 2281663 718

All patents cited herein above are incorporated herein in theirentirety. To the extent that any conflict in disclosure may exist, thepresent disclosure shall control. Various modifications and alterationsof this disclosure may be made by those skilled in the art withoutdeparting from the scope and spirit of this disclosure, and it should beunderstood that this disclosure is not to be unduly limited to theillustrative embodiments set forth herein.

1-51. (canceled)
 52. A method comprising: providing a layer of ceramicprecursor material supported on a carrier, wherein the layer of ceramicprecursor material comprises a ceramic precursor and free water, whereinthe ceramic precursor comprises an alpha alumina precursor; and cuttingthrough the layer of ceramic precursor material using a laser beam toprovide shaped ceramic precursor particles.
 53. The method of claim 52,further comprising: drying the shaped ceramic precursor particles toprovide dried shaped ceramic precursor particles; calcining the driedshaped ceramic precursor particles to provide calcined shaped ceramicprecursor particles; impregnating the calcined shaped ceramic precursorparticles with an impregnating composition comprising a mixturecomprising a second liquid medium and at least one of a metal oxide orprecursor thereof to provide impregnated calcined shaped ceramicprecursor particles, wherein the impregnating composition impregnatesthe calcined shaped ceramic precursor particles to a lesser degree onsurfaces formed by the cutting of the laser beam than other surfaces ofthe calcined shaped ceramic precursor particles
 54. The method of claim53, further comprising: sintering the impregnated calcined shapedceramic precursor particles to provide shaped ceramic abrasiveparticles.
 55. A method comprising: providing a layer of ceramicprecursor material supported on a carrier, wherein the layer of ceramicprecursor material comprises a ceramic precursor and free water; andscoring the layer of ceramic precursor material using a laser beam toprovide a scored layer of ceramic precursor material.
 56. The method ofclaim 55, further comprising: breaking the scored layer of ceramicprecursor material along score lines to provide shaped ceramic precursorparticles; calcining the shaped ceramic precursor particles to providecalcined shaped ceramic precursor particles; and sintering the calcinedshaped ceramic precursor particles to provide shaped ceramic abrasiveparticles.
 57. The method of claim 56, wherein the scored layer ofceramic precursor material is scored such that it forms a close-packedarray of latent abrasive precursor particles joined to one another alongscore lines in the layer of ceramic precursor material.
 58. The methodof claim 57, further comprising: forming boundary lines in theclose-packed array of latent abrasive precursor particles by cuttingthrough the layer of ceramic precursor material using the laser beam,wherein the boundary lines separate portions of the close-packed arrayof latent ceramic precursor particles.
 59. The method of claim 58,further comprising: deforming the carrier such that the portions of theclose-packed array of latent abrasive precursor particles break along atleast some of the score lines to form the shaped ceramic precursorparticles.
 60. The method of claim 55, further comprising: drying thescored layer of ceramic precursor material to provide a dried scoredlayer of ceramic precursor material; breaking the dried scored layer ofceramic precursor material along score lines to provide dried shapedceramic precursor particles; calcining the dried shaped ceramicprecursor particles to provide calcined shaped ceramic precursorparticles; and sintering the calcined shaped ceramic precursor particlesto provide shaped ceramic abrasive particles.
 61. The method of claim60, wherein the layer of ceramic precursor material is scored such thatit forms a close-packed array of latent dried ceramic precursorparticles joined to one another along score lines in the layer ofceramic precursor material.
 62. The method of claim 61, furthercomprising: forming boundary lines in the close-packed array of latentdried ceramic precursor particles by cutting through the layer ofceramic precursor material using the laser beam, wherein the boundarylines separate portions of the close-packed array of latent driedceramic precursor particles.
 63. The method of claim 62, wherein saidbreaking the scored layer of ceramic precursor material along scorelines is caused at least in part by deforming the carrier such that theportions of the close-packed array of latent ceramic precursor particlesbreak along at least some of the score lines to form the dried shapedceramic precursor particles.
 64. The method of claim 56, wherein theshaped ceramic abrasive particles comprise alpha-alumina-based shapedceramic abrasive particles.
 65. The method of claim 55, wherein theceramic precursor material further comprises an absorber that absorbsincident electromagnetic radiation of the laser beam and converts itinto heat.
 66. Shaped ceramic abrasive particles prepared according tothe method of claim
 52. 67. Shaped ceramic abrasive particles, whereineach of the shaped ceramic abrasive particles independently comprises abody member and at least three rod-shaped members extending from thebody member.
 68. The shaped ceramic abrasive particles of claim 67,wherein each one of the at least three rod-shaped members has across-sectional profile independently selected from a circle, anellipse, a square, a rectangle, or a triangle.
 69. The shaped ceramicabrasive particles of claim 67, wherein the at least three rod-shapedmembers are out of plane with the body member, and wherein the at leastthree rod-shaped members extend from the same side of the body member.70. The shaped ceramic abrasive particles of claim 67, wherein theshaped ceramic abrasive particles comprise alpha-alumina.
 71. The shapedceramic abrasive particles of claim 67, wherein the body member has anopening therein.
 72. The shaped ceramic abrasive particles of claim 67,wherein said at least three rod-shaped members comprises first, second,third, fourth, fifth, six, seventh, and eighth rod-shaped members. 73.The shaped ceramic abrasive particles of claim 67, wherein the shapedceramic abrasive particles comprise alpha-alumina.
 74. The shapedceramic abrasive particles of claim 67, wherein the shaped ceramicabrasive particles have a size distribution corresponding to anabrasives industry recognized nominal grade.
 75. Shaped ceramic abrasiveparticles, wherein each of the shaped ceramic abrasive particles has abody portion bounded by a peripheral loop portion having a roughenedsurface texture as compared to the body portion.
 76. The shaped ceramicabrasive particles of claim 75, wherein the shaped ceramic abrasiveparticles have a size distribution corresponding to an abrasivesindustry recognized nominal grade.
 77. The shaped ceramic abrasiveparticles of claim 75, wherein the shaped ceramic abrasive particlescomprise alpha-alumina.
 78. Shaped ceramic precursor particles, whereinthe shaped ceramic precursor particles have a peripheral loop portionencircling and abutting an interior portion, and wherein the peripheralloop portion comprises alpha alumina, and the interior portion comprisesan alpha alumina precursor and is free of alpha alumina.
 79. The shapedceramic precursor particles of claim 78, wherein the alpha aluminaprecursor comprises a boehmite gel.
 80. Shaped ceramic precursorparticles, wherein each of the shaped ceramic precursor particles hasfirst and second opposed nonadjacent major surfaces, a peripheralsurface extending between the first and second major surfaces, whereinthe peripheral surface comprises an ablated region extending along theperipheral surface adjacent to the first major surface but notcontacting the second major surface, and a fractured region extendingalong the peripheral surface adjacent the second major surface but notcontacting the first major surface.
 81. The shaped ceramic precursorparticles of claim 80, wherein the fractured region has an area greaterthan that of the ablated region.
 82. The shaped ceramic precursorparticles of claim 80, wherein the shaped ceramic precursor particlescomprise an alpha alumina precursor.
 83. Shaped ceramic abrasiveparticles, wherein each of the shaped ceramic abrasive particles hasfirst and second opposed nonadjacent major surfaces, a peripheralsurface extending between the first and second major surfaces, whereinthe peripheral surface comprises an ablated region extending along theperipheral surface adjacent to the first major surface but notcontacting the second major surface, and a fractured region extendingalong the peripheral surface adjacent the second major surface but notcontacting the first major surface.
 84. The shaped ceramic abrasiveparticles of claim 83, wherein the fractured region has an area greaterthan that of the ablated region.
 85. The shaped ceramic abrasiveparticles of claim 83, wherein the shaped ceramic abrasive particlescomprise alpha alumina.
 86. The shaped ceramic abrasive particles ofclaim 83, wherein the shaped ceramic abrasive particles have a sizedistribution corresponding to an abrasives industry recognized nominalgrade.
 87. A bonded abrasive article comprising the shaped ceramicabrasive particles of claim 83 retained in a binder.
 88. Shaped ceramicabrasive particles, wherein each of the shaped ceramic abrasiveparticles comprises first and second opposed major surfaces that areconnected by first and second opposed sides and first and second opposedends, wherein the first and second opposed major surfaces aresubstantially smooth, wherein the first and second opposed sides and thefirst and second opposed ends have a surface topography comprisingtortuous rounded micrometer-scale projections and depressions, whereinthe first side abuts the first major surface forming an acute dihedralangle, and wherein the second side abuts the first major surface formingobtuse dihedral angle.